* [PATCH v2 0/3] Fixes for CVE-2021-3998 and CVE-2021-3999
@ 2022-01-19 8:21 Siddhesh Poyarekar
2022-01-19 8:21 ` [PATCH v2 1/3] support: Add helpers to create paths longer than PATH_MAX Siddhesh Poyarekar
` (3 more replies)
0 siblings, 4 replies; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-19 8:21 UTC (permalink / raw)
To: libc-alpha
Add functions to make directory trees with paths longer than PATH_MAX
and use them to test fixes for CVE-2021-3998 and CVE-2021-3999.
Tested on x86_64 and i686.
Changes from v1:
- Try reducing directory name size to meet lower limits of some fuse
filesystems
- Fixed review comments
- Credited Qualys in NEWS
- Use x* functions wherever possible
- Drop size check in linux getcwd implementation and rely only on the
posix one to flag the error
- Fix formatting issues I had missed before.
Siddhesh Poyarekar (3):
support: Add helpers to create paths longer than PATH_MAX
realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX
[BZ #28770]
getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999)
NEWS | 10 +
stdlib/Makefile | 1 +
stdlib/canonicalize.c | 12 +-
stdlib/tst-realpath-toolong.c | 49 ++++
support/temp_file.c | 173 ++++++++++++-
support/temp_file.h | 9 +
sysdeps/posix/getcwd.c | 7 +
sysdeps/unix/sysv/linux/Makefile | 7 +-
.../unix/sysv/linux/tst-getcwd-smallbuff.c | 245 ++++++++++++++++++
9 files changed, 501 insertions(+), 12 deletions(-)
create mode 100644 stdlib/tst-realpath-toolong.c
create mode 100644 sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
--
2.34.1
^ permalink raw reply [flat|nested] 36+ messages in thread
* [PATCH v2 1/3] support: Add helpers to create paths longer than PATH_MAX
2022-01-19 8:21 [PATCH v2 0/3] Fixes for CVE-2021-3998 and CVE-2021-3999 Siddhesh Poyarekar
@ 2022-01-19 8:21 ` Siddhesh Poyarekar
2022-01-19 10:13 ` Siddhesh Poyarekar
2022-01-19 8:21 ` [PATCH v2 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX (CVE-2021-3998) Siddhesh Poyarekar
` (2 subsequent siblings)
3 siblings, 1 reply; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-19 8:21 UTC (permalink / raw)
To: libc-alpha
Add new helpers support_create_and_chdir_toolong_temp_directory and
support_chdir_toolong_temp_directory to create and descend into
directory trees longer than PATH_MAX.
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
support/temp_file.c | 173 +++++++++++++++++++++++++++++++++++++++++---
support/temp_file.h | 9 +++
2 files changed, 173 insertions(+), 9 deletions(-)
diff --git a/support/temp_file.c b/support/temp_file.c
index e7bb8aadb9..59060e573f 100644
--- a/support/temp_file.c
+++ b/support/temp_file.c
@@ -1,5 +1,6 @@
/* Temporary file handling for tests.
Copyright (C) 1998-2022 Free Software Foundation, Inc.
+ Copyright The GNU Tools Authors.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -20,15 +21,17 @@
some 32-bit platforms. */
#define _FILE_OFFSET_BITS 64
+#include <support/check.h>
#include <support/temp_file.h>
#include <support/temp_file-internal.h>
#include <support/support.h>
+#include <errno.h>
#include <paths.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
-#include <unistd.h>
+#include <xunistd.h>
/* List of temporary files. */
static struct temp_name_list
@@ -36,14 +39,32 @@ static struct temp_name_list
struct temp_name_list *next;
char *name;
pid_t owner;
+ bool toolong;
} *temp_name_list;
/* Location of the temporary files. Set by the test skeleton via
support_set_test_dir. The string is not be freed. */
static const char *test_dir = _PATH_TMP;
-void
-add_temp_file (const char *name)
+/* Name of subdirectories in a too long temporary directory tree. */
+static char *toolong_subdir;
+static bool toolong_subdir_initialized;
+
+/* Return the maximum size of path on the target. */
+static inline size_t
+get_path_max (void)
+{
+#ifdef PATH_MAX
+ return PATH_MAX;
+#else
+ size_t path_max = pathconf ("/", _PC_PATH_MAX);
+ return (path_max < 0 ? 1024
+ : path_max <= PTRDIFF_MAX ? path_max : PTRDIFF_MAX);
+#endif
+}
+
+static void
+add_temp_file_internal (const char *name, bool toolong)
{
struct temp_name_list *newp
= (struct temp_name_list *) xcalloc (sizeof (*newp), 1);
@@ -53,12 +74,19 @@ add_temp_file (const char *name)
newp->name = newname;
newp->next = temp_name_list;
newp->owner = getpid ();
+ newp->toolong = toolong;
temp_name_list = newp;
}
else
free (newp);
}
+void
+add_temp_file (const char *name)
+{
+ add_temp_file_internal (name, false);
+}
+
int
create_temp_file_in_dir (const char *base, const char *dir, char **filename)
{
@@ -90,8 +118,8 @@ create_temp_file (const char *base, char **filename)
return create_temp_file_in_dir (base, test_dir, filename);
}
-char *
-support_create_temp_directory (const char *base)
+static char *
+create_temp_directory_internal (const char *base, bool toolong)
{
char *path = xasprintf ("%s/%sXXXXXX", test_dir, base);
if (mkdtemp (path) == NULL)
@@ -99,16 +127,132 @@ support_create_temp_directory (const char *base)
printf ("error: mkdtemp (\"%s\"): %m", path);
exit (1);
}
- add_temp_file (path);
+ add_temp_file_internal (path, toolong);
return path;
}
-/* Helper functions called by the test skeleton follow. */
+char *
+support_create_temp_directory (const char *base)
+{
+ return create_temp_directory_internal (base, false);
+}
+
+static void
+ensure_toolong_subdir_initialized (void)
+{
+ if (!toolong_subdir_initialized)
+ FAIL_EXIT1 ("uninitialized toolong directory tree\n");
+}
+
+static void
+initialize_toolong_subdir (void)
+{
+ size_t sz = NAME_MAX;
+ char testname[NAME_MAX];
+ int ret;
+
+ if (toolong_subdir_initialized)
+ return;
+
+ memset (testname, 'X', sz - 1);
+
+ /* Explore the name limit on the file system. This should typically be
+ NAME_MAX, but it could be less on some fuse filesystems. */
+ do
+ {
+ struct stat statbuf;
+
+ testname[sz - 1] = '\0';
+ ret = stat (testname, &statbuf);
+ }
+ while (ret != 0 && errno == ENAMETOOLONG && (sz = sz / 2) > 0);
+
+ if (ret != 0 && errno == ENAMETOOLONG)
+ FAIL_EXIT1 ("stat (%s) failed with ENAMETOOLONG\n", testname);
+
+ toolong_subdir = xmalloc (sz);
+ strcpy (toolong_subdir, testname);
+ toolong_subdir_initialized = true;
+}
+
+char *
+support_create_and_chdir_toolong_temp_directory (const char *basename)
+{
+ size_t path_max = get_path_max ();
+
+ char *base = create_temp_directory_internal (basename, true);
+
+ xchdir (base);
+
+ initialize_toolong_subdir ();
+
+ size_t sz = strlen (toolong_subdir);
+
+ /* Create directories and descend into them so that the final path is larger
+ than PATH_MAX. */
+ for (size_t i = 0; i <= path_max / sz; i++)
+ {
+ xmkdir (toolong_subdir, S_IRWXU);
+ xchdir (toolong_subdir);
+ }
+ return base;
+}
void
-support_set_test_dir (const char *path)
+support_chdir_toolong_temp_directory (const char *base)
{
- test_dir = path;
+ size_t path_max = get_path_max ();
+ ensure_toolong_subdir_initialized ();
+
+ xchdir (base);
+
+ size_t sz = strlen (toolong_subdir);
+ for (size_t i = 0; i <= path_max / sz; i++)
+ xchdir (toolong_subdir);
+}
+
+/* Helper functions called by the test skeleton follow. */
+
+static void
+remove_toolong_subdirs (const char *base)
+{
+ size_t path_max = get_path_max ();
+
+ ensure_toolong_subdir_initialized ();
+
+ if (chdir (base) != 0)
+ {
+ printf ("warning: toolong cleanup base failed: chdir (\"%s\"): %m\n",
+ base);
+ return;
+ }
+
+ /* Descend. */
+ int levels = 0;
+ size_t sz = strlen (toolong_subdir);
+ for (levels = 0; levels <= path_max / sz; levels++)
+ if (chdir (toolong_subdir) != 0)
+ {
+ printf ("warning: toolong cleanup failed: chdir (\"%s\"): %m\n",
+ toolong_subdir);
+ return;
+ }
+
+ /* Ascend and remove. */
+ while (--levels >= 0)
+ {
+ if (chdir ("..") != 0)
+ {
+ printf ("warning: toolong cleanup failed: chdir (\"..\"): %m\n");
+ return;
+ }
+ if (remove (toolong_subdir) != 0)
+ {
+ printf ("warning: could not remove subdirectory: %s: %m\n",
+ toolong_subdir);
+ return;
+ }
+ }
}
void
@@ -123,6 +267,9 @@ support_delete_temp_files (void)
around, to prevent PID reuse.) */
if (temp_name_list->owner == pid)
{
+ if (temp_name_list->toolong)
+ remove_toolong_subdirs (temp_name_list->name);
+
if (remove (temp_name_list->name) != 0)
printf ("warning: could not remove temporary file: %s: %m\n",
temp_name_list->name);
@@ -133,6 +280,8 @@ support_delete_temp_files (void)
free (temp_name_list);
temp_name_list = next;
}
+
+ free (toolong_subdir);
}
void
@@ -147,3 +296,9 @@ support_print_temp_files (FILE *f)
fprintf (f, ")\n");
}
}
+
+void
+support_set_test_dir (const char *path)
+{
+ test_dir = path;
+}
diff --git a/support/temp_file.h b/support/temp_file.h
index 50a443abe4..8459ddda72 100644
--- a/support/temp_file.h
+++ b/support/temp_file.h
@@ -44,6 +44,15 @@ int create_temp_file_in_dir (const char *base, const char *dir,
returns. The caller should free this string. */
char *support_create_temp_directory (const char *base);
+/* Create a temporary directory tree that is longer than PATH_MAX and schedule
+ it for deletion. BASENAME is used as a prefix for the unique directory
+ name, which the function returns. The caller should free this string. */
+char *support_create_and_chdir_toolong_temp_directory (const char *basename);
+
+/* Change into the innermost directory of the directory tree BASE, which was
+ created using support_create_and_chdir_toolong_temp_directory. */
+void support_chdir_toolong_temp_directory (const char *base);
+
__END_DECLS
#endif /* SUPPORT_TEMP_FILE_H */
--
2.34.1
^ permalink raw reply [flat|nested] 36+ messages in thread
* [PATCH v2 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX (CVE-2021-3998)
2022-01-19 8:21 [PATCH v2 0/3] Fixes for CVE-2021-3998 and CVE-2021-3999 Siddhesh Poyarekar
2022-01-19 8:21 ` [PATCH v2 1/3] support: Add helpers to create paths longer than PATH_MAX Siddhesh Poyarekar
@ 2022-01-19 8:21 ` Siddhesh Poyarekar
2022-01-19 8:21 ` [PATCH v2 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999) Siddhesh Poyarekar
2022-01-20 9:32 ` [PATCH v3 0/3] Fixes for CVE-2021-3998 and CVE-2021-3999 Siddhesh Poyarekar
3 siblings, 0 replies; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-19 8:21 UTC (permalink / raw)
To: libc-alpha
realpath returns an allocated string when the result exceeds PATH_MAX,
which is unexpected when its second argument is not NULL. This results
in the second argument (resolved) being uninitialized and also results
in a memory leak since the caller expects resolved to be the same as the
returned value.
Return NULL and set errno to ENAMETOOLONG if the result exceeds
PATH_MAX. This fixes BZ #28770, which is CVE-2021-3998.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
NEWS | 4 +++
stdlib/Makefile | 1 +
stdlib/canonicalize.c | 12 +++++++--
stdlib/tst-realpath-toolong.c | 49 +++++++++++++++++++++++++++++++++++
4 files changed, 64 insertions(+), 2 deletions(-)
create mode 100644 stdlib/tst-realpath-toolong.c
diff --git a/NEWS b/NEWS
index 6ed9fa9787..4c392a445e 100644
--- a/NEWS
+++ b/NEWS
@@ -166,6 +166,10 @@ Security related changes:
CVE-2022-23218: Passing an overlong file name to the svcunix_create
legacy function could result in a stack-based buffer overflow.
+ CVE-2021-3998: Passing a path longer than PATH_MAX to the realpath
+ function could result in a memory leak and potential access of
+ uninitialized memory. Reported by Qualys.
+
The following bugs are resolved with this release:
[The release manager will add the list generated by
diff --git a/stdlib/Makefile b/stdlib/Makefile
index 1e81f98fac..8236741984 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -109,6 +109,7 @@ tests := \
tst-random \
tst-random2 \
tst-realpath \
+ tst-realpath-toolong \
tst-secure-getenv \
tst-setcontext \
tst-setcontext2 \
diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
index f36bdf4c76..732dc7ea46 100644
--- a/stdlib/canonicalize.c
+++ b/stdlib/canonicalize.c
@@ -400,8 +400,16 @@ realpath_stk (const char *name, char *resolved,
error:
*dest++ = '\0';
- if (resolved != NULL && dest - rname <= get_path_max ())
- rname = strcpy (resolved, rname);
+ if (resolved != NULL)
+ {
+ if (dest - rname <= get_path_max ())
+ rname = strcpy (resolved, rname);
+ else
+ {
+ failed = true;
+ __set_errno (ENAMETOOLONG);
+ }
+ }
error_nomem:
scratch_buffer_free (&extra_buffer);
diff --git a/stdlib/tst-realpath-toolong.c b/stdlib/tst-realpath-toolong.c
new file mode 100644
index 0000000000..8bed772460
--- /dev/null
+++ b/stdlib/tst-realpath-toolong.c
@@ -0,0 +1,49 @@
+/* Verify that realpath returns NULL with ENAMETOOLONG if the result exceeds
+ NAME_MAX.
+ Copyright The GNU Toolchain Authors.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <errno.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <support/check.h>
+#include <support/temp_file.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#define BASENAME "tst-realpath-toolong."
+
+int
+do_test (void)
+{
+ char *base = support_create_and_chdir_toolong_temp_directory (BASENAME);
+
+ char buf[PATH_MAX + 1];
+ const char *res = realpath (".", buf);
+
+ /* canonicalize.c states that if the real path is >= PATH_MAX, then
+ realpath returns NULL and sets ENAMETOOLONG. */
+ TEST_VERIFY (res == NULL);
+ TEST_VERIFY (errno == ENAMETOOLONG);
+
+ free (base);
+ return 0;
+}
+
+#include <support/test-driver.c>
--
2.34.1
^ permalink raw reply [flat|nested] 36+ messages in thread
* [PATCH v2 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999)
2022-01-19 8:21 [PATCH v2 0/3] Fixes for CVE-2021-3998 and CVE-2021-3999 Siddhesh Poyarekar
2022-01-19 8:21 ` [PATCH v2 1/3] support: Add helpers to create paths longer than PATH_MAX Siddhesh Poyarekar
2022-01-19 8:21 ` [PATCH v2 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX (CVE-2021-3998) Siddhesh Poyarekar
@ 2022-01-19 8:21 ` Siddhesh Poyarekar
2022-01-20 9:32 ` [PATCH v3 0/3] Fixes for CVE-2021-3998 and CVE-2021-3999 Siddhesh Poyarekar
3 siblings, 0 replies; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-19 8:21 UTC (permalink / raw)
To: libc-alpha; +Cc: adhemerval.zanella, eggert, Qualys Security Advisory
No valid path returned by getcwd would fit into 1 byte, so reject the
size early and return NULL with errno set to ERANGE. This change is
prompted by CVE-2021-3999, which describes a single byte buffer
underflow and overflow when all of the following conditions are met:
- The buffer size (i.e. the second argument of getcwd) is 1 byte
- The current working directory is too long
- '/' is also mounted on the current working directory
Sequence of events:
- In sysdeps/unix/sysv/linux/getcwd.c, the syscall returns ENAMETOOLONG
because the linux kernel checks for name length before it checks
buffer size
- The code falls back to the generic getcwd in sysdeps/posix
- In the generic func, the buf[0] is set to '\0' on line 250
- this while loop on line 262 is bypassed:
while (!(thisdev == rootdev && thisino == rootino))
since the rootfs (/) is bind mounted onto the directory and the flow
goes on to line 449, where it puts a '/' in the byte before the
buffer.
- Finally on line 458, it moves 2 bytes (the underflowed byte and the
'\0') to the buf[0] and buf[1], resulting in a 1 byte buffer overflow.
- buf is returned on line 469 and errno is not set.
This resolves BZ #28769.
Signed-off-by: Qualys Security Advisory <qsa@qualys.com>
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
NEWS | 6 +
sysdeps/posix/getcwd.c | 7 +
sysdeps/unix/sysv/linux/Makefile | 7 +-
.../unix/sysv/linux/tst-getcwd-smallbuff.c | 245 ++++++++++++++++++
4 files changed, 264 insertions(+), 1 deletion(-)
create mode 100644 sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
diff --git a/NEWS b/NEWS
index 4c392a445e..07e9eac52d 100644
--- a/NEWS
+++ b/NEWS
@@ -170,6 +170,12 @@ Security related changes:
function could result in a memory leak and potential access of
uninitialized memory. Reported by Qualys.
+ CVE-2021-3999: Passing a buffer of size exactly 1 byte to the getcwd
+ function may result in an off-by-one buffer underflow and overflow
+ when the current working directory is longer than PATH_MAX and also
+ corresponds to the / directory through an unprivileged mount
+ namespace. Reported by Qualys.
+
The following bugs are resolved with this release:
[The release manager will add the list generated by
diff --git a/sysdeps/posix/getcwd.c b/sysdeps/posix/getcwd.c
index e147a31a81..9d5787b6f4 100644
--- a/sysdeps/posix/getcwd.c
+++ b/sysdeps/posix/getcwd.c
@@ -187,6 +187,13 @@ __getcwd_generic (char *buf, size_t size)
size_t allocated = size;
size_t used;
+ /* A size of 1 byte is never useful. */
+ if (allocated == 1)
+ {
+ __set_errno (ERANGE);
+ return NULL;
+ }
+
#if HAVE_MINIMALLY_WORKING_GETCWD
/* If AT_FDCWD is not defined, the algorithm below is O(N**2) and
this is much slower than the system getcwd (at least on
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 85fc8cbf75..7ca9350c99 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -346,7 +346,12 @@ sysdep_routines += xstatconv internal_statvfs \
sysdep_headers += bits/fcntl-linux.h
-tests += tst-fallocate tst-fallocate64 tst-o_path-locks
+tests += \
+ tst-fallocate \
+ tst-fallocate64 \
+ tst-getcwd-smallbuff \
+ tst-o_path-locks \
+# tests
endif
ifeq ($(subdir),elf)
diff --git a/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
new file mode 100644
index 0000000000..791dfe4d02
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
@@ -0,0 +1,245 @@
+/* Verify that getcwd returns ERANGE for size 1 byte and does not underflow
+ buffer when the CWD is too long and is also a mount target of /. See bug
+ #28769 or CVE-2021-3999 for more context.
+ Copyright The GNU Toolchain Authors.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <support/check.h>
+#include <support/temp_file.h>
+#include <support/xsched.h>
+#include <support/xunistd.h>
+
+#ifndef PATH_MAX
+# define PATH_MAX 1024
+#endif
+
+static char *base;
+#define BASENAME "tst-getcwd-smallbuff"
+#define MOUNT_NAME "mpoint"
+static int sockfd[2];
+
+static void
+do_cleanup (void)
+{
+ support_chdir_toolong_temp_directory (base);
+ TEST_VERIFY_EXIT (rmdir (MOUNT_NAME) == 0);
+ free (base);
+}
+
+static void
+send_fd (const int sock, const int fd)
+{
+ struct msghdr msg;
+ union
+ {
+ struct cmsghdr hdr;
+ char buf[CMSG_SPACE (sizeof (int))];
+ } cmsgbuf;
+ struct cmsghdr *cmsg;
+ struct iovec vec;
+ char ch = 'A';
+ ssize_t n;
+
+ memset (&msg, 0, sizeof (msg));
+ memset (&cmsgbuf, 0, sizeof (cmsgbuf));
+ msg.msg_control = &cmsgbuf.buf;
+ msg.msg_controllen = sizeof (cmsgbuf.buf);
+
+ cmsg = CMSG_FIRSTHDR (&msg);
+ cmsg->cmsg_len = CMSG_LEN (sizeof (int));
+ cmsg->cmsg_level = SOL_SOCKET;
+ cmsg->cmsg_type = SCM_RIGHTS;
+ *(int *) CMSG_DATA (cmsg) = fd;
+
+ vec.iov_base = &ch;
+ vec.iov_len = 1;
+ msg.msg_iov = &vec;
+ msg.msg_iovlen = 1;
+
+ while ((n = sendmsg (sock, &msg, 0)) == -1 && errno == EINTR);
+
+ TEST_VERIFY_EXIT (n == 1);
+}
+
+static int
+recv_fd (const int sock)
+{
+ struct msghdr msg;
+ union
+ {
+ struct cmsghdr hdr;
+ char buf[CMSG_SPACE(sizeof(int))];
+ } cmsgbuf;
+ struct cmsghdr *cmsg;
+ struct iovec vec;
+ ssize_t n;
+ char ch = '\0';
+ int fd = -1;
+
+ memset (&msg, 0, sizeof (msg));
+ vec.iov_base = &ch;
+ vec.iov_len = 1;
+ msg.msg_iov = &vec;
+ msg.msg_iovlen = 1;
+
+ memset (&cmsgbuf, 0, sizeof (cmsgbuf));
+ msg.msg_control = &cmsgbuf.buf;
+ msg.msg_controllen = sizeof (cmsgbuf.buf);
+
+ while ((n = recvmsg (sock, &msg, 0)) == -1 && errno == EINTR);
+ if (n != 1 || ch != 'A')
+ return -1;
+
+ cmsg = CMSG_FIRSTHDR (&msg);
+ if (cmsg == NULL)
+ return -1;
+ if (cmsg->cmsg_type != SCM_RIGHTS)
+ return -1;
+ fd = *(const int *) CMSG_DATA (cmsg);
+ if (fd < 0)
+ return -1;
+ return fd;
+}
+
+static int
+child_func (void * const arg)
+{
+ xclose (sockfd[0]);
+ const int sock = sockfd[1];
+ char ch;
+
+ TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
+ TEST_VERIFY_EXIT (ch == '1');
+
+ if (mount ("/", MOUNT_NAME, NULL, MS_BIND | MS_REC, NULL))
+ FAIL_EXIT1 ("mount failed: %m\n");
+ const int fd = xopen ("mpoint",
+ O_RDONLY | O_PATH | O_DIRECTORY | O_NOFOLLOW, 0);
+
+ send_fd (sock, fd);
+ xclose (fd);
+
+ TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
+ TEST_VERIFY_EXIT (ch == 'a');
+
+ xclose (sock);
+ return 0;
+}
+
+static void
+update_map (char * const mapping, const char * const map_file)
+{
+ const size_t map_len = strlen (mapping);
+
+ const int fd = xopen (map_file, O_WRONLY, 0);
+ xwrite (fd, mapping, map_len);
+ xclose (fd);
+}
+
+static void
+proc_setgroups_write (const long child_pid, const char * const str)
+{
+ const size_t str_len = strlen(str);
+
+ char setgroups_path[64];
+ snprintf (setgroups_path, sizeof (setgroups_path),
+ "/proc/%ld/setgroups", child_pid);
+
+ const int fd = open (setgroups_path, O_WRONLY);
+
+ if (fd < 0)
+ {
+ TEST_VERIFY_EXIT (errno == ENOENT);
+ FAIL_UNSUPPORTED ("/proc/%ld/setgroups not found\n", child_pid);
+ }
+
+ xwrite (fd, str, str_len);
+ xclose(fd);
+}
+
+static char child_stack[1024 * 1024];
+
+int
+do_test (void)
+{
+ base = support_create_and_chdir_toolong_temp_directory (BASENAME);
+
+ xmkdir (MOUNT_NAME, S_IRWXU);
+ atexit (do_cleanup);
+
+ TEST_VERIFY_EXIT (socketpair (AF_UNIX, SOCK_STREAM, 0, sockfd) == 0);
+ pid_t child_pid = xclone (child_func, NULL, child_stack,
+ sizeof (child_stack),
+ CLONE_NEWUSER | CLONE_NEWNS | SIGCHLD);
+
+ xclose (sockfd[1]);
+ const int sock = sockfd[0];
+
+ char map_path[64], map_buf[64];
+ snprintf (map_path, sizeof (map_path), "/proc/%ld/uid_map",
+ (long) child_pid);
+ snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getuid());
+ update_map (map_buf, map_path);
+
+ proc_setgroups_write ((long) child_pid, "deny");
+ snprintf (map_path, sizeof (map_path), "/proc/%ld/gid_map",
+ (long) child_pid);
+ snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getgid());
+ update_map (map_buf, map_path);
+
+ TEST_VERIFY_EXIT (send (sock, "1", 1, MSG_NOSIGNAL) == 1);
+ const int fd = recv_fd (sock);
+ TEST_VERIFY_EXIT (fd >= 0);
+ TEST_VERIFY_EXIT (fchdir (fd) == 0);
+
+ static char buf[2 * 10 + 1];
+ memset (buf, 'A', sizeof(buf));
+
+ /* Finally, call getcwd and check if it resulted in a buffer underflow. */
+ char * cwd = getcwd (buf + sizeof(buf) / 2, 1);
+ TEST_VERIFY (cwd == NULL);
+ TEST_VERIFY (errno == ERANGE);
+
+ for (int i = 0; i < sizeof (buf); i++)
+ if (buf[i] != 'A')
+ {
+ printf ("buf[%d] = %02x\n", i, (unsigned int) buf[i]);
+ support_record_failure ();
+ }
+
+ TEST_VERIFY_EXIT (send (sock, "a", 1, MSG_NOSIGNAL) == 1);
+ xclose (sock);
+ TEST_VERIFY_EXIT (xwaitpid (child_pid, NULL, 0) == child_pid);
+
+ return 0;
+}
+
+#define CLEANUP_HANDLER do_cleanup
+#include <support/test-driver.c>
--
2.34.1
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v2 1/3] support: Add helpers to create paths longer than PATH_MAX
2022-01-19 8:21 ` [PATCH v2 1/3] support: Add helpers to create paths longer than PATH_MAX Siddhesh Poyarekar
@ 2022-01-19 10:13 ` Siddhesh Poyarekar
2022-01-20 14:47 ` Cristian Rodríguez
0 siblings, 1 reply; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-19 10:13 UTC (permalink / raw)
To: Siddhesh Poyarekar, libc-alpha
On 19/01/2022 13:51, Siddhesh Poyarekar via Libc-alpha wrote:
> Add new helpers support_create_and_chdir_toolong_temp_directory and
> support_chdir_toolong_temp_directory to create and descend into
> directory trees longer than PATH_MAX.
>
> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
> ---
> support/temp_file.c | 173 +++++++++++++++++++++++++++++++++++++++++---
> support/temp_file.h | 9 +++
> 2 files changed, 173 insertions(+), 9 deletions(-)
>
> diff --git a/support/temp_file.c b/support/temp_file.c
> index e7bb8aadb9..59060e573f 100644
> --- a/support/temp_file.c
> +++ b/support/temp_file.c
> @@ -1,5 +1,6 @@
> /* Temporary file handling for tests.
> Copyright (C) 1998-2022 Free Software Foundation, Inc.
> + Copyright The GNU Tools Authors.
> This file is part of the GNU C Library.
>
> The GNU C Library is free software; you can redistribute it and/or
> @@ -20,15 +21,17 @@
> some 32-bit platforms. */
> #define _FILE_OFFSET_BITS 64
>
> +#include <support/check.h>
> #include <support/temp_file.h>
> #include <support/temp_file-internal.h>
> #include <support/support.h>
>
> +#include <errno.h>
> #include <paths.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> -#include <unistd.h>
> +#include <xunistd.h>
>
> /* List of temporary files. */
> static struct temp_name_list
> @@ -36,14 +39,32 @@ static struct temp_name_list
> struct temp_name_list *next;
> char *name;
> pid_t owner;
> + bool toolong;
> } *temp_name_list;
>
> /* Location of the temporary files. Set by the test skeleton via
> support_set_test_dir. The string is not be freed. */
> static const char *test_dir = _PATH_TMP;
>
> -void
> -add_temp_file (const char *name)
> +/* Name of subdirectories in a too long temporary directory tree. */
> +static char *toolong_subdir;
> +static bool toolong_subdir_initialized;
> +
> +/* Return the maximum size of path on the target. */
> +static inline size_t
> +get_path_max (void)
> +{
> +#ifdef PATH_MAX
> + return PATH_MAX;
> +#else
> + size_t path_max = pathconf ("/", _PC_PATH_MAX);
> + return (path_max < 0 ? 1024
> + : path_max <= PTRDIFF_MAX ? path_max : PTRDIFF_MAX);
> +#endif
> +}
> +
> +static void
> +add_temp_file_internal (const char *name, bool toolong)
> {
> struct temp_name_list *newp
> = (struct temp_name_list *) xcalloc (sizeof (*newp), 1);
> @@ -53,12 +74,19 @@ add_temp_file (const char *name)
> newp->name = newname;
> newp->next = temp_name_list;
> newp->owner = getpid ();
> + newp->toolong = toolong;
> temp_name_list = newp;
> }
> else
> free (newp);
> }
>
> +void
> +add_temp_file (const char *name)
> +{
> + add_temp_file_internal (name, false);
> +}
> +
> int
> create_temp_file_in_dir (const char *base, const char *dir, char **filename)
> {
> @@ -90,8 +118,8 @@ create_temp_file (const char *base, char **filename)
> return create_temp_file_in_dir (base, test_dir, filename);
> }
>
> -char *
> -support_create_temp_directory (const char *base)
> +static char *
> +create_temp_directory_internal (const char *base, bool toolong)
> {
> char *path = xasprintf ("%s/%sXXXXXX", test_dir, base);
> if (mkdtemp (path) == NULL)
> @@ -99,16 +127,132 @@ support_create_temp_directory (const char *base)
> printf ("error: mkdtemp (\"%s\"): %m", path);
> exit (1);
> }
> - add_temp_file (path);
> + add_temp_file_internal (path, toolong);
> return path;
> }
>
> -/* Helper functions called by the test skeleton follow. */
> +char *
> +support_create_temp_directory (const char *base)
> +{
> + return create_temp_directory_internal (base, false);
> +}
> +
> +static void
> +ensure_toolong_subdir_initialized (void)
> +{
> + if (!toolong_subdir_initialized)
> + FAIL_EXIT1 ("uninitialized toolong directory tree\n");
> +}
> +
> +static void
> +initialize_toolong_subdir (void)
> +{
> + size_t sz = NAME_MAX;
> + char testname[NAME_MAX];
> + int ret;
> +
> + if (toolong_subdir_initialized)
> + return;
> +
> + memset (testname, 'X', sz - 1);
> +
> + /* Explore the name limit on the file system. This should typically be
> + NAME_MAX, but it could be less on some fuse filesystems. */
> + do
> + {
> + struct stat statbuf;
> +
> + testname[sz - 1] = '\0';
> + ret = stat (testname, &statbuf);
> + }
> + while (ret != 0 && errno == ENAMETOOLONG && (sz = sz / 2) > 0);
> +
> + if (ret != 0 && errno == ENAMETOOLONG)
> + FAIL_EXIT1 ("stat (%s) failed with ENAMETOOLONG\n", testname);
> +
> + toolong_subdir = xmalloc (sz);
> + strcpy (toolong_subdir, testname);
> + toolong_subdir_initialized = true;
> +}
> +
> +char *
> +support_create_and_chdir_toolong_temp_directory (const char *basename)
> +{
> + size_t path_max = get_path_max ();
> +
> + char *base = create_temp_directory_internal (basename, true);
> +
> + xchdir (base);
> +
> + initialize_toolong_subdir ();
> +
> + size_t sz = strlen (toolong_subdir);
> +
> + /* Create directories and descend into them so that the final path is larger
> + than PATH_MAX. */
> + for (size_t i = 0; i <= path_max / sz; i++)
> + {
> + xmkdir (toolong_subdir, S_IRWXU);
This still doesn't work on the trybot, which somehow fails with
ENAMETOOLONG even though stat() on that length worked in
initialize_toolong_subdir. I'm going to need to reproduce the
environment properly to figure out what's going on.
Siddhesh
> + xchdir (toolong_subdir);
> + }
> + return base;
> +}
>
> void
> -support_set_test_dir (const char *path)
> +support_chdir_toolong_temp_directory (const char *base)
> {
> - test_dir = path;
> + size_t path_max = get_path_max ();
> + ensure_toolong_subdir_initialized ();
> +
> + xchdir (base);
> +
> + size_t sz = strlen (toolong_subdir);
> + for (size_t i = 0; i <= path_max / sz; i++)
> + xchdir (toolong_subdir);
> +}
> +
> +/* Helper functions called by the test skeleton follow. */
> +
> +static void
> +remove_toolong_subdirs (const char *base)
> +{
> + size_t path_max = get_path_max ();
> +
> + ensure_toolong_subdir_initialized ();
> +
> + if (chdir (base) != 0)
> + {
> + printf ("warning: toolong cleanup base failed: chdir (\"%s\"): %m\n",
> + base);
> + return;
> + }
> +
> + /* Descend. */
> + int levels = 0;
> + size_t sz = strlen (toolong_subdir);
> + for (levels = 0; levels <= path_max / sz; levels++)
> + if (chdir (toolong_subdir) != 0)
> + {
> + printf ("warning: toolong cleanup failed: chdir (\"%s\"): %m\n",
> + toolong_subdir);
> + return;
> + }
> +
> + /* Ascend and remove. */
> + while (--levels >= 0)
> + {
> + if (chdir ("..") != 0)
> + {
> + printf ("warning: toolong cleanup failed: chdir (\"..\"): %m\n");
> + return;
> + }
> + if (remove (toolong_subdir) != 0)
> + {
> + printf ("warning: could not remove subdirectory: %s: %m\n",
> + toolong_subdir);
> + return;
> + }
> + }
> }
>
> void
> @@ -123,6 +267,9 @@ support_delete_temp_files (void)
> around, to prevent PID reuse.) */
> if (temp_name_list->owner == pid)
> {
> + if (temp_name_list->toolong)
> + remove_toolong_subdirs (temp_name_list->name);
> +
> if (remove (temp_name_list->name) != 0)
> printf ("warning: could not remove temporary file: %s: %m\n",
> temp_name_list->name);
> @@ -133,6 +280,8 @@ support_delete_temp_files (void)
> free (temp_name_list);
> temp_name_list = next;
> }
> +
> + free (toolong_subdir);
> }
>
> void
> @@ -147,3 +296,9 @@ support_print_temp_files (FILE *f)
> fprintf (f, ")\n");
> }
> }
> +
> +void
> +support_set_test_dir (const char *path)
> +{
> + test_dir = path;
> +}
> diff --git a/support/temp_file.h b/support/temp_file.h
> index 50a443abe4..8459ddda72 100644
> --- a/support/temp_file.h
> +++ b/support/temp_file.h
> @@ -44,6 +44,15 @@ int create_temp_file_in_dir (const char *base, const char *dir,
> returns. The caller should free this string. */
> char *support_create_temp_directory (const char *base);
>
> +/* Create a temporary directory tree that is longer than PATH_MAX and schedule
> + it for deletion. BASENAME is used as a prefix for the unique directory
> + name, which the function returns. The caller should free this string. */
> +char *support_create_and_chdir_toolong_temp_directory (const char *basename);
> +
> +/* Change into the innermost directory of the directory tree BASE, which was
> + created using support_create_and_chdir_toolong_temp_directory. */
> +void support_chdir_toolong_temp_directory (const char *base);
> +
> __END_DECLS
>
> #endif /* SUPPORT_TEMP_FILE_H */
^ permalink raw reply [flat|nested] 36+ messages in thread
* [PATCH v3 0/3] Fixes for CVE-2021-3998 and CVE-2021-3999
2022-01-19 8:21 [PATCH v2 0/3] Fixes for CVE-2021-3998 and CVE-2021-3999 Siddhesh Poyarekar
` (2 preceding siblings ...)
2022-01-19 8:21 ` [PATCH v2 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999) Siddhesh Poyarekar
@ 2022-01-20 9:32 ` Siddhesh Poyarekar
2022-01-20 9:32 ` [PATCH v3 1/3] support: Add helpers to create paths longer than PATH_MAX Siddhesh Poyarekar
` (2 more replies)
3 siblings, 3 replies; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-20 9:32 UTC (permalink / raw)
To: libc-alpha; +Cc: eggert, adhemerval.zanella, fweimer
Add functions to make directory trees with paths longer than PATH_MAX
and use them to test fixes for CVE-2021-3998 and CVE-2021-3999.
Tested on x86_64 and i686.
Changes from v2:
- Adjusted test infrastructure to bail out if the filesystem does not support
creating directory trees greater than PATH_MAX.
Changes from v1:
- Try reducing directory name size to meet lower limits of some fuse
filesystems
- Fixed review comments
- Credited Qualys in NEWS
- Use x* functions wherever possible
- Drop size check in linux getcwd implementation and rely only on the
posix one to flag the error
- Fix formatting issues I had missed before.
Siddhesh Poyarekar (3):
support: Add helpers to create paths longer than PATH_MAX
realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX
[BZ #28770]
getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999)
NEWS | 10 +
stdlib/Makefile | 1 +
stdlib/canonicalize.c | 12 +-
stdlib/tst-realpath-toolong.c | 49 ++++
support/temp_file.c | 159 +++++++++++-
support/temp_file.h | 9 +
sysdeps/posix/getcwd.c | 7 +
sysdeps/unix/sysv/linux/Makefile | 7 +-
.../unix/sysv/linux/tst-getcwd-smallbuff.c | 245 ++++++++++++++++++
9 files changed, 487 insertions(+), 12 deletions(-)
create mode 100644 stdlib/tst-realpath-toolong.c
create mode 100644 sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
--
2.34.1
^ permalink raw reply [flat|nested] 36+ messages in thread
* [PATCH v3 1/3] support: Add helpers to create paths longer than PATH_MAX
2022-01-20 9:32 ` [PATCH v3 0/3] Fixes for CVE-2021-3998 and CVE-2021-3999 Siddhesh Poyarekar
@ 2022-01-20 9:32 ` Siddhesh Poyarekar
2022-01-21 16:27 ` Adhemerval Zanella
2022-01-20 9:32 ` [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770] Siddhesh Poyarekar
2022-01-20 9:32 ` [PATCH v3 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999) Siddhesh Poyarekar
2 siblings, 1 reply; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-20 9:32 UTC (permalink / raw)
To: libc-alpha; +Cc: eggert, adhemerval.zanella, fweimer
Add new helpers support_create_and_chdir_toolong_temp_directory and
support_chdir_toolong_temp_directory to create and descend into
directory trees longer than PATH_MAX.
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
support/temp_file.c | 159 +++++++++++++++++++++++++++++++++++++++++---
support/temp_file.h | 9 +++
2 files changed, 159 insertions(+), 9 deletions(-)
diff --git a/support/temp_file.c b/support/temp_file.c
index e7bb8aadb9..e41128c2d4 100644
--- a/support/temp_file.c
+++ b/support/temp_file.c
@@ -1,5 +1,6 @@
/* Temporary file handling for tests.
Copyright (C) 1998-2022 Free Software Foundation, Inc.
+ Copyright The GNU Tools Authors.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -20,15 +21,17 @@
some 32-bit platforms. */
#define _FILE_OFFSET_BITS 64
+#include <support/check.h>
#include <support/temp_file.h>
#include <support/temp_file-internal.h>
#include <support/support.h>
+#include <errno.h>
#include <paths.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
-#include <unistd.h>
+#include <xunistd.h>
/* List of temporary files. */
static struct temp_name_list
@@ -36,14 +39,20 @@ static struct temp_name_list
struct temp_name_list *next;
char *name;
pid_t owner;
+ bool toolong;
} *temp_name_list;
/* Location of the temporary files. Set by the test skeleton via
support_set_test_dir. The string is not be freed. */
static const char *test_dir = _PATH_TMP;
-void
-add_temp_file (const char *name)
+/* Name of subdirectories in a too long temporary directory tree. */
+static char toolong_subdir[NAME_MAX + 1];
+static bool toolong_initialized;
+static size_t toolong_path_max;
+
+static void
+add_temp_file_internal (const char *name, bool toolong)
{
struct temp_name_list *newp
= (struct temp_name_list *) xcalloc (sizeof (*newp), 1);
@@ -53,12 +62,19 @@ add_temp_file (const char *name)
newp->name = newname;
newp->next = temp_name_list;
newp->owner = getpid ();
+ newp->toolong = toolong;
temp_name_list = newp;
}
else
free (newp);
}
+void
+add_temp_file (const char *name)
+{
+ add_temp_file_internal (name, false);
+}
+
int
create_temp_file_in_dir (const char *base, const char *dir, char **filename)
{
@@ -90,8 +106,8 @@ create_temp_file (const char *base, char **filename)
return create_temp_file_in_dir (base, test_dir, filename);
}
-char *
-support_create_temp_directory (const char *base)
+static char *
+create_temp_directory_internal (const char *base, bool toolong)
{
char *path = xasprintf ("%s/%sXXXXXX", test_dir, base);
if (mkdtemp (path) == NULL)
@@ -99,16 +115,132 @@ support_create_temp_directory (const char *base)
printf ("error: mkdtemp (\"%s\"): %m", path);
exit (1);
}
- add_temp_file (path);
+ add_temp_file_internal (path, toolong);
return path;
}
-/* Helper functions called by the test skeleton follow. */
+char *
+support_create_temp_directory (const char *base)
+{
+ return create_temp_directory_internal (base, false);
+}
+
+static void
+ensure_toolong_initialized (void)
+{
+ if (!toolong_initialized)
+ FAIL_EXIT1 ("uninitialized toolong directory tree\n");
+}
+
+static void
+initialize_toolong (const char *base)
+{
+ long name_max = pathconf (base, _PC_NAME_MAX);
+ name_max = (name_max < 0 ? 64
+ : (name_max < sizeof (toolong_subdir) ? name_max
+ : sizeof (toolong_subdir) - 1));
+
+ long path_max = pathconf (base, _PC_PATH_MAX);
+ path_max = (path_max < 0 ? 1024
+ : path_max <= PTRDIFF_MAX ? path_max : PTRDIFF_MAX);
+
+ /* Sanity check to ensure that the test does not create temporary directories
+ in different filesystems because this API doesn't support it. */
+ if (toolong_initialized)
+ {
+ if (name_max != strlen (toolong_subdir))
+ FAIL_UNSUPPORTED ("name_max: Temporary directories in different"
+ " filesystems not supported yet\n");
+ if (path_max != toolong_path_max)
+ FAIL_UNSUPPORTED ("path_max: Temporary directories in different"
+ " filesystems not supported yet\n");
+ return;
+ }
+
+ toolong_path_max = path_max;
+
+ size_t len = name_max;
+ memset (toolong_subdir, 'X', len);
+ toolong_initialized = true;
+}
+
+char *
+support_create_and_chdir_toolong_temp_directory (const char *basename)
+{
+ char *base = create_temp_directory_internal (basename, true);
+ xchdir (base);
+
+ initialize_toolong (base);
+
+ size_t sz = strlen (toolong_subdir);
+
+ /* Create directories and descend into them so that the final path is larger
+ than PATH_MAX. */
+ for (size_t i = 0; i <= toolong_path_max / sz; i++)
+ {
+ int ret = mkdir (toolong_subdir, S_IRWXU);
+ if (ret != 0 && errno == ENAMETOOLONG)
+ FAIL_UNSUPPORTED ("Filesystem does not support creating too long "
+ "directory trees\n");
+ else if (ret != 0)
+ FAIL_EXIT1 ("Failed to create directory tree: %m\n");
+ xchdir (toolong_subdir);
+ }
+ return base;
+}
void
-support_set_test_dir (const char *path)
+support_chdir_toolong_temp_directory (const char *base)
{
- test_dir = path;
+ ensure_toolong_initialized ();
+
+ xchdir (base);
+
+ size_t sz = strlen (toolong_subdir);
+ for (size_t i = 0; i <= toolong_path_max / sz; i++)
+ xchdir (toolong_subdir);
+}
+
+/* Helper functions called by the test skeleton follow. */
+
+static void
+remove_toolong_subdirs (const char *base)
+{
+ ensure_toolong_initialized ();
+
+ if (chdir (base) != 0)
+ {
+ printf ("warning: toolong cleanup base failed: chdir (\"%s\"): %m\n",
+ base);
+ return;
+ }
+
+ /* Descend. */
+ int levels = 0;
+ size_t sz = strlen (toolong_subdir);
+ for (levels = 0; levels <= toolong_path_max / sz; levels++)
+ if (chdir (toolong_subdir) != 0)
+ {
+ printf ("warning: toolong cleanup failed: chdir (\"%s\"): %m\n",
+ toolong_subdir);
+ break;
+ }
+
+ /* Ascend and remove. */
+ while (--levels >= 0)
+ {
+ if (chdir ("..") != 0)
+ {
+ printf ("warning: toolong cleanup failed: chdir (\"..\"): %m\n");
+ return;
+ }
+ if (remove (toolong_subdir) != 0)
+ {
+ printf ("warning: could not remove subdirectory: %s: %m\n",
+ toolong_subdir);
+ return;
+ }
+ }
}
void
@@ -123,6 +255,9 @@ support_delete_temp_files (void)
around, to prevent PID reuse.) */
if (temp_name_list->owner == pid)
{
+ if (temp_name_list->toolong)
+ remove_toolong_subdirs (temp_name_list->name);
+
if (remove (temp_name_list->name) != 0)
printf ("warning: could not remove temporary file: %s: %m\n",
temp_name_list->name);
@@ -147,3 +282,9 @@ support_print_temp_files (FILE *f)
fprintf (f, ")\n");
}
}
+
+void
+support_set_test_dir (const char *path)
+{
+ test_dir = path;
+}
diff --git a/support/temp_file.h b/support/temp_file.h
index 50a443abe4..8459ddda72 100644
--- a/support/temp_file.h
+++ b/support/temp_file.h
@@ -44,6 +44,15 @@ int create_temp_file_in_dir (const char *base, const char *dir,
returns. The caller should free this string. */
char *support_create_temp_directory (const char *base);
+/* Create a temporary directory tree that is longer than PATH_MAX and schedule
+ it for deletion. BASENAME is used as a prefix for the unique directory
+ name, which the function returns. The caller should free this string. */
+char *support_create_and_chdir_toolong_temp_directory (const char *basename);
+
+/* Change into the innermost directory of the directory tree BASE, which was
+ created using support_create_and_chdir_toolong_temp_directory. */
+void support_chdir_toolong_temp_directory (const char *base);
+
__END_DECLS
#endif /* SUPPORT_TEMP_FILE_H */
--
2.34.1
^ permalink raw reply [flat|nested] 36+ messages in thread
* [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770]
2022-01-20 9:32 ` [PATCH v3 0/3] Fixes for CVE-2021-3998 and CVE-2021-3999 Siddhesh Poyarekar
2022-01-20 9:32 ` [PATCH v3 1/3] support: Add helpers to create paths longer than PATH_MAX Siddhesh Poyarekar
@ 2022-01-20 9:32 ` Siddhesh Poyarekar
2022-01-21 23:22 ` Joseph Myers
2022-01-24 13:45 ` [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770] Andreas Schwab
2022-01-20 9:32 ` [PATCH v3 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999) Siddhesh Poyarekar
2 siblings, 2 replies; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-20 9:32 UTC (permalink / raw)
To: libc-alpha; +Cc: eggert, adhemerval.zanella, fweimer
realpath returns an allocated string when the result exceeds PATH_MAX,
which is unexpected when its second argument is not NULL. This results
in the second argument (resolved) being uninitialized and also results
in a memory leak since the caller expects resolved to be the same as the
returned value.
Return NULL and set errno to ENAMETOOLONG if the result exceeds
PATH_MAX. This fixes [BZ #28770], which is CVE-2021-3998.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
NEWS | 4 +++
stdlib/Makefile | 1 +
stdlib/canonicalize.c | 12 +++++++--
stdlib/tst-realpath-toolong.c | 49 +++++++++++++++++++++++++++++++++++
4 files changed, 64 insertions(+), 2 deletions(-)
create mode 100644 stdlib/tst-realpath-toolong.c
diff --git a/NEWS b/NEWS
index 6ed9fa9787..4c392a445e 100644
--- a/NEWS
+++ b/NEWS
@@ -166,6 +166,10 @@ Security related changes:
CVE-2022-23218: Passing an overlong file name to the svcunix_create
legacy function could result in a stack-based buffer overflow.
+ CVE-2021-3998: Passing a path longer than PATH_MAX to the realpath
+ function could result in a memory leak and potential access of
+ uninitialized memory. Reported by Qualys.
+
The following bugs are resolved with this release:
[The release manager will add the list generated by
diff --git a/stdlib/Makefile b/stdlib/Makefile
index 1e81f98fac..8236741984 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -109,6 +109,7 @@ tests := \
tst-random \
tst-random2 \
tst-realpath \
+ tst-realpath-toolong \
tst-secure-getenv \
tst-setcontext \
tst-setcontext2 \
diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
index f36bdf4c76..732dc7ea46 100644
--- a/stdlib/canonicalize.c
+++ b/stdlib/canonicalize.c
@@ -400,8 +400,16 @@ realpath_stk (const char *name, char *resolved,
error:
*dest++ = '\0';
- if (resolved != NULL && dest - rname <= get_path_max ())
- rname = strcpy (resolved, rname);
+ if (resolved != NULL)
+ {
+ if (dest - rname <= get_path_max ())
+ rname = strcpy (resolved, rname);
+ else
+ {
+ failed = true;
+ __set_errno (ENAMETOOLONG);
+ }
+ }
error_nomem:
scratch_buffer_free (&extra_buffer);
diff --git a/stdlib/tst-realpath-toolong.c b/stdlib/tst-realpath-toolong.c
new file mode 100644
index 0000000000..8bed772460
--- /dev/null
+++ b/stdlib/tst-realpath-toolong.c
@@ -0,0 +1,49 @@
+/* Verify that realpath returns NULL with ENAMETOOLONG if the result exceeds
+ NAME_MAX.
+ Copyright The GNU Toolchain Authors.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <errno.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <support/check.h>
+#include <support/temp_file.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#define BASENAME "tst-realpath-toolong."
+
+int
+do_test (void)
+{
+ char *base = support_create_and_chdir_toolong_temp_directory (BASENAME);
+
+ char buf[PATH_MAX + 1];
+ const char *res = realpath (".", buf);
+
+ /* canonicalize.c states that if the real path is >= PATH_MAX, then
+ realpath returns NULL and sets ENAMETOOLONG. */
+ TEST_VERIFY (res == NULL);
+ TEST_VERIFY (errno == ENAMETOOLONG);
+
+ free (base);
+ return 0;
+}
+
+#include <support/test-driver.c>
--
2.34.1
^ permalink raw reply [flat|nested] 36+ messages in thread
* [PATCH v3 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999)
2022-01-20 9:32 ` [PATCH v3 0/3] Fixes for CVE-2021-3998 and CVE-2021-3999 Siddhesh Poyarekar
2022-01-20 9:32 ` [PATCH v3 1/3] support: Add helpers to create paths longer than PATH_MAX Siddhesh Poyarekar
2022-01-20 9:32 ` [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770] Siddhesh Poyarekar
@ 2022-01-20 9:32 ` Siddhesh Poyarekar
2022-01-20 13:32 ` Andreas Schwab
2022-01-21 16:41 ` Adhemerval Zanella
2 siblings, 2 replies; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-20 9:32 UTC (permalink / raw)
To: libc-alpha; +Cc: eggert, adhemerval.zanella, fweimer, Qualys Security Advisory
No valid path returned by getcwd would fit into 1 byte, so reject the
size early and return NULL with errno set to ERANGE. This change is
prompted by CVE-2021-3999, which describes a single byte buffer
underflow and overflow when all of the following conditions are met:
- The buffer size (i.e. the second argument of getcwd) is 1 byte
- The current working directory is too long
- '/' is also mounted on the current working directory
Sequence of events:
- In sysdeps/unix/sysv/linux/getcwd.c, the syscall returns ENAMETOOLONG
because the linux kernel checks for name length before it checks
buffer size
- The code falls back to the generic getcwd in sysdeps/posix
- In the generic func, the buf[0] is set to '\0' on line 250
- this while loop on line 262 is bypassed:
while (!(thisdev == rootdev && thisino == rootino))
since the rootfs (/) is bind mounted onto the directory and the flow
goes on to line 449, where it puts a '/' in the byte before the
buffer.
- Finally on line 458, it moves 2 bytes (the underflowed byte and the
'\0') to the buf[0] and buf[1], resulting in a 1 byte buffer overflow.
- buf is returned on line 469 and errno is not set.
This resolves BZ #28769.
Signed-off-by: Qualys Security Advisory <qsa@qualys.com>
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
NEWS | 6 +
sysdeps/posix/getcwd.c | 7 +
sysdeps/unix/sysv/linux/Makefile | 7 +-
.../unix/sysv/linux/tst-getcwd-smallbuff.c | 245 ++++++++++++++++++
4 files changed, 264 insertions(+), 1 deletion(-)
create mode 100644 sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
diff --git a/NEWS b/NEWS
index 4c392a445e..07e9eac52d 100644
--- a/NEWS
+++ b/NEWS
@@ -170,6 +170,12 @@ Security related changes:
function could result in a memory leak and potential access of
uninitialized memory. Reported by Qualys.
+ CVE-2021-3999: Passing a buffer of size exactly 1 byte to the getcwd
+ function may result in an off-by-one buffer underflow and overflow
+ when the current working directory is longer than PATH_MAX and also
+ corresponds to the / directory through an unprivileged mount
+ namespace. Reported by Qualys.
+
The following bugs are resolved with this release:
[The release manager will add the list generated by
diff --git a/sysdeps/posix/getcwd.c b/sysdeps/posix/getcwd.c
index e147a31a81..9d5787b6f4 100644
--- a/sysdeps/posix/getcwd.c
+++ b/sysdeps/posix/getcwd.c
@@ -187,6 +187,13 @@ __getcwd_generic (char *buf, size_t size)
size_t allocated = size;
size_t used;
+ /* A size of 1 byte is never useful. */
+ if (allocated == 1)
+ {
+ __set_errno (ERANGE);
+ return NULL;
+ }
+
#if HAVE_MINIMALLY_WORKING_GETCWD
/* If AT_FDCWD is not defined, the algorithm below is O(N**2) and
this is much slower than the system getcwd (at least on
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 85fc8cbf75..7ca9350c99 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -346,7 +346,12 @@ sysdep_routines += xstatconv internal_statvfs \
sysdep_headers += bits/fcntl-linux.h
-tests += tst-fallocate tst-fallocate64 tst-o_path-locks
+tests += \
+ tst-fallocate \
+ tst-fallocate64 \
+ tst-getcwd-smallbuff \
+ tst-o_path-locks \
+# tests
endif
ifeq ($(subdir),elf)
diff --git a/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
new file mode 100644
index 0000000000..791dfe4d02
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
@@ -0,0 +1,245 @@
+/* Verify that getcwd returns ERANGE for size 1 byte and does not underflow
+ buffer when the CWD is too long and is also a mount target of /. See bug
+ #28769 or CVE-2021-3999 for more context.
+ Copyright The GNU Toolchain Authors.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <support/check.h>
+#include <support/temp_file.h>
+#include <support/xsched.h>
+#include <support/xunistd.h>
+
+#ifndef PATH_MAX
+# define PATH_MAX 1024
+#endif
+
+static char *base;
+#define BASENAME "tst-getcwd-smallbuff"
+#define MOUNT_NAME "mpoint"
+static int sockfd[2];
+
+static void
+do_cleanup (void)
+{
+ support_chdir_toolong_temp_directory (base);
+ TEST_VERIFY_EXIT (rmdir (MOUNT_NAME) == 0);
+ free (base);
+}
+
+static void
+send_fd (const int sock, const int fd)
+{
+ struct msghdr msg;
+ union
+ {
+ struct cmsghdr hdr;
+ char buf[CMSG_SPACE (sizeof (int))];
+ } cmsgbuf;
+ struct cmsghdr *cmsg;
+ struct iovec vec;
+ char ch = 'A';
+ ssize_t n;
+
+ memset (&msg, 0, sizeof (msg));
+ memset (&cmsgbuf, 0, sizeof (cmsgbuf));
+ msg.msg_control = &cmsgbuf.buf;
+ msg.msg_controllen = sizeof (cmsgbuf.buf);
+
+ cmsg = CMSG_FIRSTHDR (&msg);
+ cmsg->cmsg_len = CMSG_LEN (sizeof (int));
+ cmsg->cmsg_level = SOL_SOCKET;
+ cmsg->cmsg_type = SCM_RIGHTS;
+ *(int *) CMSG_DATA (cmsg) = fd;
+
+ vec.iov_base = &ch;
+ vec.iov_len = 1;
+ msg.msg_iov = &vec;
+ msg.msg_iovlen = 1;
+
+ while ((n = sendmsg (sock, &msg, 0)) == -1 && errno == EINTR);
+
+ TEST_VERIFY_EXIT (n == 1);
+}
+
+static int
+recv_fd (const int sock)
+{
+ struct msghdr msg;
+ union
+ {
+ struct cmsghdr hdr;
+ char buf[CMSG_SPACE(sizeof(int))];
+ } cmsgbuf;
+ struct cmsghdr *cmsg;
+ struct iovec vec;
+ ssize_t n;
+ char ch = '\0';
+ int fd = -1;
+
+ memset (&msg, 0, sizeof (msg));
+ vec.iov_base = &ch;
+ vec.iov_len = 1;
+ msg.msg_iov = &vec;
+ msg.msg_iovlen = 1;
+
+ memset (&cmsgbuf, 0, sizeof (cmsgbuf));
+ msg.msg_control = &cmsgbuf.buf;
+ msg.msg_controllen = sizeof (cmsgbuf.buf);
+
+ while ((n = recvmsg (sock, &msg, 0)) == -1 && errno == EINTR);
+ if (n != 1 || ch != 'A')
+ return -1;
+
+ cmsg = CMSG_FIRSTHDR (&msg);
+ if (cmsg == NULL)
+ return -1;
+ if (cmsg->cmsg_type != SCM_RIGHTS)
+ return -1;
+ fd = *(const int *) CMSG_DATA (cmsg);
+ if (fd < 0)
+ return -1;
+ return fd;
+}
+
+static int
+child_func (void * const arg)
+{
+ xclose (sockfd[0]);
+ const int sock = sockfd[1];
+ char ch;
+
+ TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
+ TEST_VERIFY_EXIT (ch == '1');
+
+ if (mount ("/", MOUNT_NAME, NULL, MS_BIND | MS_REC, NULL))
+ FAIL_EXIT1 ("mount failed: %m\n");
+ const int fd = xopen ("mpoint",
+ O_RDONLY | O_PATH | O_DIRECTORY | O_NOFOLLOW, 0);
+
+ send_fd (sock, fd);
+ xclose (fd);
+
+ TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
+ TEST_VERIFY_EXIT (ch == 'a');
+
+ xclose (sock);
+ return 0;
+}
+
+static void
+update_map (char * const mapping, const char * const map_file)
+{
+ const size_t map_len = strlen (mapping);
+
+ const int fd = xopen (map_file, O_WRONLY, 0);
+ xwrite (fd, mapping, map_len);
+ xclose (fd);
+}
+
+static void
+proc_setgroups_write (const long child_pid, const char * const str)
+{
+ const size_t str_len = strlen(str);
+
+ char setgroups_path[64];
+ snprintf (setgroups_path, sizeof (setgroups_path),
+ "/proc/%ld/setgroups", child_pid);
+
+ const int fd = open (setgroups_path, O_WRONLY);
+
+ if (fd < 0)
+ {
+ TEST_VERIFY_EXIT (errno == ENOENT);
+ FAIL_UNSUPPORTED ("/proc/%ld/setgroups not found\n", child_pid);
+ }
+
+ xwrite (fd, str, str_len);
+ xclose(fd);
+}
+
+static char child_stack[1024 * 1024];
+
+int
+do_test (void)
+{
+ base = support_create_and_chdir_toolong_temp_directory (BASENAME);
+
+ xmkdir (MOUNT_NAME, S_IRWXU);
+ atexit (do_cleanup);
+
+ TEST_VERIFY_EXIT (socketpair (AF_UNIX, SOCK_STREAM, 0, sockfd) == 0);
+ pid_t child_pid = xclone (child_func, NULL, child_stack,
+ sizeof (child_stack),
+ CLONE_NEWUSER | CLONE_NEWNS | SIGCHLD);
+
+ xclose (sockfd[1]);
+ const int sock = sockfd[0];
+
+ char map_path[64], map_buf[64];
+ snprintf (map_path, sizeof (map_path), "/proc/%ld/uid_map",
+ (long) child_pid);
+ snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getuid());
+ update_map (map_buf, map_path);
+
+ proc_setgroups_write ((long) child_pid, "deny");
+ snprintf (map_path, sizeof (map_path), "/proc/%ld/gid_map",
+ (long) child_pid);
+ snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getgid());
+ update_map (map_buf, map_path);
+
+ TEST_VERIFY_EXIT (send (sock, "1", 1, MSG_NOSIGNAL) == 1);
+ const int fd = recv_fd (sock);
+ TEST_VERIFY_EXIT (fd >= 0);
+ TEST_VERIFY_EXIT (fchdir (fd) == 0);
+
+ static char buf[2 * 10 + 1];
+ memset (buf, 'A', sizeof(buf));
+
+ /* Finally, call getcwd and check if it resulted in a buffer underflow. */
+ char * cwd = getcwd (buf + sizeof(buf) / 2, 1);
+ TEST_VERIFY (cwd == NULL);
+ TEST_VERIFY (errno == ERANGE);
+
+ for (int i = 0; i < sizeof (buf); i++)
+ if (buf[i] != 'A')
+ {
+ printf ("buf[%d] = %02x\n", i, (unsigned int) buf[i]);
+ support_record_failure ();
+ }
+
+ TEST_VERIFY_EXIT (send (sock, "a", 1, MSG_NOSIGNAL) == 1);
+ xclose (sock);
+ TEST_VERIFY_EXIT (xwaitpid (child_pid, NULL, 0) == child_pid);
+
+ return 0;
+}
+
+#define CLEANUP_HANDLER do_cleanup
+#include <support/test-driver.c>
--
2.34.1
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v3 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999)
2022-01-20 9:32 ` [PATCH v3 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999) Siddhesh Poyarekar
@ 2022-01-20 13:32 ` Andreas Schwab
2022-01-21 16:41 ` Adhemerval Zanella
1 sibling, 0 replies; 36+ messages in thread
From: Andreas Schwab @ 2022-01-20 13:32 UTC (permalink / raw)
To: Siddhesh Poyarekar via Libc-alpha
Cc: Siddhesh Poyarekar, fweimer, Qualys Security Advisory
Ok.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v2 1/3] support: Add helpers to create paths longer than PATH_MAX
2022-01-19 10:13 ` Siddhesh Poyarekar
@ 2022-01-20 14:47 ` Cristian Rodríguez
2022-01-20 14:56 ` Florian Weimer
2022-01-20 14:57 ` Siddhesh Poyarekar
0 siblings, 2 replies; 36+ messages in thread
From: Cristian Rodríguez @ 2022-01-20 14:47 UTC (permalink / raw)
To: Siddhesh Poyarekar; +Cc: Siddhesh Poyarekar, libc-alpha
On Wed, Jan 19, 2022 at 7:21 AM Siddhesh Poyarekar <siddhesh@gotplt.org> wrote:
>
> On 19/01/2022 13:51, Siddhesh Poyarekar via Libc-alpha wrote:
> > Add new helpers support_create_and_chdir_toolong_temp_directory and
> > support_chdir_toolong_temp_directory to create and descend into
> > directory trees longer than PATH_MAX.
Note that recentish linux kernel versions do not allow d_name 's
larger than kernel 's PATH_MAX definition, in that case getdents
returns EIO, this behavior is since kernel 5.5.
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v2 1/3] support: Add helpers to create paths longer than PATH_MAX
2022-01-20 14:47 ` Cristian Rodríguez
@ 2022-01-20 14:56 ` Florian Weimer
2022-01-20 15:17 ` Cristian Rodríguez
2022-01-20 14:57 ` Siddhesh Poyarekar
1 sibling, 1 reply; 36+ messages in thread
From: Florian Weimer @ 2022-01-20 14:56 UTC (permalink / raw)
To: Cristian Rodríguez
Cc: Siddhesh Poyarekar, Siddhesh Poyarekar, libc-alpha
* Cristian Rodríguez:
> On Wed, Jan 19, 2022 at 7:21 AM Siddhesh Poyarekar <siddhesh@gotplt.org> wrote:
>>
>> On 19/01/2022 13:51, Siddhesh Poyarekar via Libc-alpha wrote:
>> > Add new helpers support_create_and_chdir_toolong_temp_directory and
>> > support_chdir_toolong_temp_directory to create and descend into
>> > directory trees longer than PATH_MAX.
>
> Note that recentish linux kernel versions do not allow d_name 's
> larger than kernel 's PATH_MAX definition, in that case getdents
> returns EIO, this behavior is since kernel 5.5.
NAME_MAX or PATH_MAX? d_name should be capped by NAME_MAX, but
historically it is not.
Thanks,
Florian
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v2 1/3] support: Add helpers to create paths longer than PATH_MAX
2022-01-20 14:47 ` Cristian Rodríguez
2022-01-20 14:56 ` Florian Weimer
@ 2022-01-20 14:57 ` Siddhesh Poyarekar
1 sibling, 0 replies; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-20 14:57 UTC (permalink / raw)
To: Cristian Rodríguez; +Cc: libc-alpha
On 20/01/2022 20:17, Cristian Rodríguez wrote:
> On Wed, Jan 19, 2022 at 7:21 AM Siddhesh Poyarekar <siddhesh@gotplt.org> wrote:
>>
>> On 19/01/2022 13:51, Siddhesh Poyarekar via Libc-alpha wrote:
>>> Add new helpers support_create_and_chdir_toolong_temp_directory and
>>> support_chdir_toolong_temp_directory to create and descend into
>>> directory trees longer than PATH_MAX.
>
> Note that recentish linux kernel versions do not allow d_name 's
> larger than kernel 's PATH_MAX definition, in that case getdents
> returns EIO, this behavior is since kernel 5.5.
>
The d_name in these helpers is limited to _PC_NAME_MAX so AFAICT we
shouldn't run into issues with that.
Thanks,
Siddhesh
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v2 1/3] support: Add helpers to create paths longer than PATH_MAX
2022-01-20 14:56 ` Florian Weimer
@ 2022-01-20 15:17 ` Cristian Rodríguez
0 siblings, 0 replies; 36+ messages in thread
From: Cristian Rodríguez @ 2022-01-20 15:17 UTC (permalink / raw)
To: Florian Weimer; +Cc: Siddhesh Poyarekar, Siddhesh Poyarekar, libc-alpha
On Thu, Jan 20, 2022 at 11:56 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * Cristian Rodríguez:
>
> > On Wed, Jan 19, 2022 at 7:21 AM Siddhesh Poyarekar <siddhesh@gotplt.org> wrote:
> >>
> >> On 19/01/2022 13:51, Siddhesh Poyarekar via Libc-alpha wrote:
> >> > Add new helpers support_create_and_chdir_toolong_temp_directory and
> >> > support_chdir_toolong_temp_directory to create and descend into
> >> > directory trees longer than PATH_MAX.
> >
> > Note that recentish linux kernel versions do not allow d_name 's
> > larger than kernel 's PATH_MAX definition, in that case getdents
> > returns EIO, this behavior is since kernel 5.5.
>
> NAME_MAX or PATH_MAX? d_name should be capped by NAME_MAX, but
> historically it is not.
PATH_MAX.. I wrote that correctly, see
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2c6b7bcd747201441923a0d3062577a8d1fbd8f8
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v3 1/3] support: Add helpers to create paths longer than PATH_MAX
2022-01-20 9:32 ` [PATCH v3 1/3] support: Add helpers to create paths longer than PATH_MAX Siddhesh Poyarekar
@ 2022-01-21 16:27 ` Adhemerval Zanella
0 siblings, 0 replies; 36+ messages in thread
From: Adhemerval Zanella @ 2022-01-21 16:27 UTC (permalink / raw)
To: Siddhesh Poyarekar, libc-alpha; +Cc: eggert, fweimer
On 20/01/2022 06:32, Siddhesh Poyarekar wrote:
> Add new helpers support_create_and_chdir_toolong_temp_directory and
> support_chdir_toolong_temp_directory to create and descend into
> directory trees longer than PATH_MAX.
>
> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
LGTM, thanks.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> ---
> support/temp_file.c | 159 +++++++++++++++++++++++++++++++++++++++++---
> support/temp_file.h | 9 +++
> 2 files changed, 159 insertions(+), 9 deletions(-)
>
> diff --git a/support/temp_file.c b/support/temp_file.c
> index e7bb8aadb9..e41128c2d4 100644
> --- a/support/temp_file.c
> +++ b/support/temp_file.c
> @@ -1,5 +1,6 @@
> /* Temporary file handling for tests.
> Copyright (C) 1998-2022 Free Software Foundation, Inc.
> + Copyright The GNU Tools Authors.
> This file is part of the GNU C Library.
>
> The GNU C Library is free software; you can redistribute it and/or
> @@ -20,15 +21,17 @@
> some 32-bit platforms. */
> #define _FILE_OFFSET_BITS 64
>
> +#include <support/check.h>
> #include <support/temp_file.h>
> #include <support/temp_file-internal.h>
> #include <support/support.h>
>
> +#include <errno.h>
> #include <paths.h>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
> -#include <unistd.h>
> +#include <xunistd.h>
>
> /* List of temporary files. */
> static struct temp_name_list
> @@ -36,14 +39,20 @@ static struct temp_name_list
> struct temp_name_list *next;
> char *name;
> pid_t owner;
> + bool toolong;
> } *temp_name_list;
>
> /* Location of the temporary files. Set by the test skeleton via
> support_set_test_dir. The string is not be freed. */
> static const char *test_dir = _PATH_TMP;
>
> -void
> -add_temp_file (const char *name)
> +/* Name of subdirectories in a too long temporary directory tree. */
> +static char toolong_subdir[NAME_MAX + 1];
> +static bool toolong_initialized;
> +static size_t toolong_path_max;
> +
I think it is suffice for current tests, although it would need to change
if any tests requires more than one large path.
> +static void
> +add_temp_file_internal (const char *name, bool toolong)
> {
> struct temp_name_list *newp
> = (struct temp_name_list *) xcalloc (sizeof (*newp), 1);
> @@ -53,12 +62,19 @@ add_temp_file (const char *name)
> newp->name = newname;
> newp->next = temp_name_list;
> newp->owner = getpid ();
> + newp->toolong = toolong;
> temp_name_list = newp;
> }
> else
> free (newp);
> }
>
> +void
> +add_temp_file (const char *name)
> +{
> + add_temp_file_internal (name, false);
> +}
> +
> int
> create_temp_file_in_dir (const char *base, const char *dir, char **filename)
> {
> @@ -90,8 +106,8 @@ create_temp_file (const char *base, char **filename)
> return create_temp_file_in_dir (base, test_dir, filename);
> }
>
> -char *
> -support_create_temp_directory (const char *base)
> +static char *
> +create_temp_directory_internal (const char *base, bool toolong)
> {
> char *path = xasprintf ("%s/%sXXXXXX", test_dir, base);
> if (mkdtemp (path) == NULL)
> @@ -99,16 +115,132 @@ support_create_temp_directory (const char *base)
> printf ("error: mkdtemp (\"%s\"): %m", path);
> exit (1);
> }
> - add_temp_file (path);
> + add_temp_file_internal (path, toolong);
> return path;
> }
>
> -/* Helper functions called by the test skeleton follow. */
> +char *
> +support_create_temp_directory (const char *base)
> +{
> + return create_temp_directory_internal (base, false);
> +}
> +
> +static void
> +ensure_toolong_initialized (void)
> +{
> + if (!toolong_initialized)
> + FAIL_EXIT1 ("uninitialized toolong directory tree\n");
> +}
> +
> +static void
> +initialize_toolong (const char *base)
> +{
> + long name_max = pathconf (base, _PC_NAME_MAX);
> + name_max = (name_max < 0 ? 64
> + : (name_max < sizeof (toolong_subdir) ? name_max
> + : sizeof (toolong_subdir) - 1));
> +
> + long path_max = pathconf (base, _PC_PATH_MAX);
> + path_max = (path_max < 0 ? 1024
> + : path_max <= PTRDIFF_MAX ? path_max : PTRDIFF_MAX);
> +
> + /* Sanity check to ensure that the test does not create temporary directories
> + in different filesystems because this API doesn't support it. */
> + if (toolong_initialized)
> + {
> + if (name_max != strlen (toolong_subdir))
> + FAIL_UNSUPPORTED ("name_max: Temporary directories in different"
> + " filesystems not supported yet\n");
> + if (path_max != toolong_path_max)
> + FAIL_UNSUPPORTED ("path_max: Temporary directories in different"
> + " filesystems not supported yet\n");
> + return;
> + }
> +
> + toolong_path_max = path_max;
> +
> + size_t len = name_max;
> + memset (toolong_subdir, 'X', len);
> + toolong_initialized = true;
> +}
> +
Ok.
> +char *
> +support_create_and_chdir_toolong_temp_directory (const char *basename)
> +{> + char *base = create_temp_directory_internal (basename, true);
> + xchdir (base);
> +
> + initialize_toolong (base);
> +
> + size_t sz = strlen (toolong_subdir);
> +
> + /* Create directories and descend into them so that the final path is larger
> + than PATH_MAX. */
> + for (size_t i = 0; i <= toolong_path_max / sz; i++)
> + {
> + int ret = mkdir (toolong_subdir, S_IRWXU);
> + if (ret != 0 && errno == ENAMETOOLONG)
> + FAIL_UNSUPPORTED ("Filesystem does not support creating too long "
> + "directory trees\n");
> + else if (ret != 0)
> + FAIL_EXIT1 ("Failed to create directory tree: %m\n");
> + xchdir (toolong_subdir);
> + }
> + return base;
> +}
>
> void
> -support_set_test_dir (const char *path)
> +support_chdir_toolong_temp_directory (const char *base)
> {
> - test_dir = path;
> + ensure_toolong_initialized ();
> +
> + xchdir (base);
> +
> + size_t sz = strlen (toolong_subdir);
> + for (size_t i = 0; i <= toolong_path_max / sz; i++)
> + xchdir (toolong_subdir);
> +}
> +
> +/* Helper functions called by the test skeleton follow. */
> +
> +static void
> +remove_toolong_subdirs (const char *base)
> +{
> + ensure_toolong_initialized ();
> +
> + if (chdir (base) != 0)
> + {
> + printf ("warning: toolong cleanup base failed: chdir (\"%s\"): %m\n",
> + base);
> + return;
> + }
I think there is no much we co in such case.
> +
> + /* Descend. */
> + int levels = 0;
> + size_t sz = strlen (toolong_subdir);
> + for (levels = 0; levels <= toolong_path_max / sz; levels++)
> + if (chdir (toolong_subdir) != 0)
> + {
> + printf ("warning: toolong cleanup failed: chdir (\"%s\"): %m\n",
> + toolong_subdir);
> + break;
> + }
> +
> + /* Ascend and remove. */
> + while (--levels >= 0)
> + {
> + if (chdir ("..") != 0)
> + {
> + printf ("warning: toolong cleanup failed: chdir (\"..\"): %m\n");
> + return;
> + }
> + if (remove (toolong_subdir) != 0)
> + {
> + printf ("warning: could not remove subdirectory: %s: %m\n",
> + toolong_subdir);
> + return;
> + }
> + }
> }
>
> void
> @@ -123,6 +255,9 @@ support_delete_temp_files (void)
> around, to prevent PID reuse.) */
> if (temp_name_list->owner == pid)
> {
> + if (temp_name_list->toolong)
> + remove_toolong_subdirs (temp_name_list->name);
> +
> if (remove (temp_name_list->name) != 0)
> printf ("warning: could not remove temporary file: %s: %m\n",
> temp_name_list->name);
> @@ -147,3 +282,9 @@ support_print_temp_files (FILE *f)
> fprintf (f, ")\n");
> }
> }
> +
> +void
> +support_set_test_dir (const char *path)
> +{
> + test_dir = path;
> +}
> diff --git a/support/temp_file.h b/support/temp_file.h
> index 50a443abe4..8459ddda72 100644
> --- a/support/temp_file.h
> +++ b/support/temp_file.h
> @@ -44,6 +44,15 @@ int create_temp_file_in_dir (const char *base, const char *dir,
> returns. The caller should free this string. */
> char *support_create_temp_directory (const char *base);
>
> +/* Create a temporary directory tree that is longer than PATH_MAX and schedule
> + it for deletion. BASENAME is used as a prefix for the unique directory
> + name, which the function returns. The caller should free this string. */
> +char *support_create_and_chdir_toolong_temp_directory (const char *basename);
> +
> +/* Change into the innermost directory of the directory tree BASE, which was
> + created using support_create_and_chdir_toolong_temp_directory. */
> +void support_chdir_toolong_temp_directory (const char *base);
> +
> __END_DECLS
>
> #endif /* SUPPORT_TEMP_FILE_H */
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v3 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999)
2022-01-20 9:32 ` [PATCH v3 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999) Siddhesh Poyarekar
2022-01-20 13:32 ` Andreas Schwab
@ 2022-01-21 16:41 ` Adhemerval Zanella
2022-01-21 17:26 ` Siddhesh Poyarekar
` (2 more replies)
1 sibling, 3 replies; 36+ messages in thread
From: Adhemerval Zanella @ 2022-01-21 16:41 UTC (permalink / raw)
To: Siddhesh Poyarekar, libc-alpha; +Cc: eggert, fweimer, Qualys Security Advisory
On 20/01/2022 06:32, Siddhesh Poyarekar wrote:
> No valid path returned by getcwd would fit into 1 byte, so reject the
> size early and return NULL with errno set to ERANGE. This change is
> prompted by CVE-2021-3999, which describes a single byte buffer
> underflow and overflow when all of the following conditions are met:
>
> - The buffer size (i.e. the second argument of getcwd) is 1 byte
> - The current working directory is too long
> - '/' is also mounted on the current working directory
>
> Sequence of events:
>
> - In sysdeps/unix/sysv/linux/getcwd.c, the syscall returns ENAMETOOLONG
> because the linux kernel checks for name length before it checks
> buffer size
>
> - The code falls back to the generic getcwd in sysdeps/posix
>
> - In the generic func, the buf[0] is set to '\0' on line 250
>
> - this while loop on line 262 is bypassed:
>
> while (!(thisdev == rootdev && thisino == rootino))
>
> since the rootfs (/) is bind mounted onto the directory and the flow
> goes on to line 449, where it puts a '/' in the byte before the
> buffer.
>
> - Finally on line 458, it moves 2 bytes (the underflowed byte and the
> '\0') to the buf[0] and buf[1], resulting in a 1 byte buffer overflow.
>
> - buf is returned on line 469 and errno is not set.
>
> This resolves BZ #28769.
>
> Signed-off-by: Qualys Security Advisory <qsa@qualys.com>
> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Look good with just two fixed below for CMSG_DATA and a couple of comments.
Ok with the fixes, the comments would be good but it is a blocker.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> ---
> NEWS | 6 +
> sysdeps/posix/getcwd.c | 7 +
> sysdeps/unix/sysv/linux/Makefile | 7 +-
> .../unix/sysv/linux/tst-getcwd-smallbuff.c | 245 ++++++++++++++++++
> 4 files changed, 264 insertions(+), 1 deletion(-)
> create mode 100644 sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
>
> diff --git a/NEWS b/NEWS
> index 4c392a445e..07e9eac52d 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -170,6 +170,12 @@ Security related changes:
> function could result in a memory leak and potential access of
> uninitialized memory. Reported by Qualys.
>
> + CVE-2021-3999: Passing a buffer of size exactly 1 byte to the getcwd
> + function may result in an off-by-one buffer underflow and overflow
> + when the current working directory is longer than PATH_MAX and also
> + corresponds to the / directory through an unprivileged mount
> + namespace. Reported by Qualys.
> +
> The following bugs are resolved with this release:
>
> [The release manager will add the list generated by
> diff --git a/sysdeps/posix/getcwd.c b/sysdeps/posix/getcwd.c
> index e147a31a81..9d5787b6f4 100644
> --- a/sysdeps/posix/getcwd.c
> +++ b/sysdeps/posix/getcwd.c
> @@ -187,6 +187,13 @@ __getcwd_generic (char *buf, size_t size)
> size_t allocated = size;
> size_t used;
>
> + /* A size of 1 byte is never useful. */
> + if (allocated == 1)
> + {
> + __set_errno (ERANGE);
> + return NULL;
> + }
> +
> #if HAVE_MINIMALLY_WORKING_GETCWD
> /* If AT_FDCWD is not defined, the algorithm below is O(N**2) and
> this is much slower than the system getcwd (at least on
> diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
> index 85fc8cbf75..7ca9350c99 100644
> --- a/sysdeps/unix/sysv/linux/Makefile
> +++ b/sysdeps/unix/sysv/linux/Makefile
> @@ -346,7 +346,12 @@ sysdep_routines += xstatconv internal_statvfs \
>
> sysdep_headers += bits/fcntl-linux.h
>
> -tests += tst-fallocate tst-fallocate64 tst-o_path-locks
> +tests += \
> + tst-fallocate \
> + tst-fallocate64 \
> + tst-getcwd-smallbuff \
> + tst-o_path-locks \
> +# tests
> endif
>
> ifeq ($(subdir),elf)
> diff --git a/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
> new file mode 100644
> index 0000000000..791dfe4d02
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
> @@ -0,0 +1,245 @@
> +/* Verify that getcwd returns ERANGE for size 1 byte and does not underflow
> + buffer when the CWD is too long and is also a mount target of /. See bug
> + #28769 or CVE-2021-3999 for more context.
> + Copyright The GNU Toolchain Authors.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <https://www.gnu.org/licenses/>. */
> +
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <limits.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/mount.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +#include <sys/wait.h>
> +
> +#include <sys/socket.h>
> +#include <sys/un.h>
> +#include <support/check.h>
> +#include <support/temp_file.h>
> +#include <support/xsched.h>
> +#include <support/xunistd.h>
> +
> +#ifndef PATH_MAX
> +# define PATH_MAX 1024
> +#endif
No need since it is a Linux only test and PATH_MAX is always defined.
> +
> +static char *base;
> +#define BASENAME "tst-getcwd-smallbuff"
> +#define MOUNT_NAME "mpoint"
> +static int sockfd[2];
> +
> +static void
> +do_cleanup (void)
> +{
> + support_chdir_toolong_temp_directory (base);
> + TEST_VERIFY_EXIT (rmdir (MOUNT_NAME) == 0);
> + free (base);
> +}
> +
> +static void
> +send_fd (const int sock, const int fd)
> +{
> + struct msghdr msg;
> + union
> + {
> + struct cmsghdr hdr;
> + char buf[CMSG_SPACE (sizeof (int))];
> + } cmsgbuf;
Maybe zero-initialize both first to avoid the memset below?
> + struct cmsghdr *cmsg;
> + struct iovec vec;
> + char ch = 'A';
> + ssize_t n;
> +
> + memset (&msg, 0, sizeof (msg));
> + memset (&cmsgbuf, 0, sizeof (cmsgbuf));
> + msg.msg_control = &cmsgbuf.buf;
> + msg.msg_controllen = sizeof (cmsgbuf.buf);
> +
> + cmsg = CMSG_FIRSTHDR (&msg);
> + cmsg->cmsg_len = CMSG_LEN (sizeof (int));
> + cmsg->cmsg_level = SOL_SOCKET;
> + cmsg->cmsg_type = SCM_RIGHTS;
> + *(int *) CMSG_DATA (cmsg) = fd;
I think CMSG_DATA does not guarantee the alignment, so I think it would be
safe to use memcpy here:
memcpy (CMSG_DATA (cmsg), &fd, sizeof (fd));
> +
> + vec.iov_base = &ch;
> + vec.iov_len = 1;
> + msg.msg_iov = &vec;
> + msg.msg_iovlen = 1;
> +
> + while ((n = sendmsg (sock, &msg, 0)) == -1 && errno == EINTR);
> +
> + TEST_VERIFY_EXIT (n == 1);
> +}
> +
Ok.
> +static int
> +recv_fd (const int sock)
> +{
> + struct msghdr msg;
Maybe also zero-initialize here.
> + union
> + {
> + struct cmsghdr hdr;
> + char buf[CMSG_SPACE(sizeof(int))];
> + } cmsgbuf;
> + struct cmsghdr *cmsg;
> + struct iovec vec;
> + ssize_t n;
> + char ch = '\0';
> + int fd = -1;
> +
> + memset (&msg, 0, sizeof (msg));
> + vec.iov_base = &ch;
> + vec.iov_len = 1;
> + msg.msg_iov = &vec;
> + msg.msg_iovlen = 1;
> +
> + memset (&cmsgbuf, 0, sizeof (cmsgbuf));
> + msg.msg_control = &cmsgbuf.buf;
> + msg.msg_controllen = sizeof (cmsgbuf.buf);
> +
> + while ((n = recvmsg (sock, &msg, 0)) == -1 && errno == EINTR);
> + if (n != 1 || ch != 'A')
> + return -1;
> +
> + cmsg = CMSG_FIRSTHDR (&msg);
> + if (cmsg == NULL)
> + return -1;
> + if (cmsg->cmsg_type != SCM_RIGHTS)
> + return -1;
> + fd = *(const int *) CMSG_DATA (cmsg);
Same as before, I think you will need to copy to a temporary using memcpy.
> + if (fd < 0)
> + return -1;
> + return fd;
> +}
> +
> +static int
> +child_func (void * const arg)
> +{
> + xclose (sockfd[0]);
> + const int sock = sockfd[1];
> + char ch;
> +
> + TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
> + TEST_VERIFY_EXIT (ch == '1');
> +
> + if (mount ("/", MOUNT_NAME, NULL, MS_BIND | MS_REC, NULL))
> + FAIL_EXIT1 ("mount failed: %m\n");
> + const int fd = xopen ("mpoint",
> + O_RDONLY | O_PATH | O_DIRECTORY | O_NOFOLLOW, 0);
> +
> + send_fd (sock, fd);
> + xclose (fd);
> +
> + TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
> + TEST_VERIFY_EXIT (ch == 'a');
> +
> + xclose (sock);
> + return 0;
> +}
> +
> +static void
> +update_map (char * const mapping, const char * const map_file)
> +{
> + const size_t map_len = strlen (mapping);
> +
> + const int fd = xopen (map_file, O_WRONLY, 0);
> + xwrite (fd, mapping, map_len);
> + xclose (fd);
> +}
> +
> +static void
> +proc_setgroups_write (const long child_pid, const char * const str)
> +{
> + const size_t str_len = strlen(str);
> +
> + char setgroups_path[64];
Maybe define the size as:
/* The path is the form /proc/%ld/setgroups. */
char map_path[sizeof("/proc/setgroups") + INT_STRLEN_BOUND (long int)];
> + snprintf (setgroups_path, sizeof (setgroups_path),
> + "/proc/%ld/setgroups", child_pid);
> +
> + const int fd = open (setgroups_path, O_WRONLY);
> +
> + if (fd < 0)
> + {
> + TEST_VERIFY_EXIT (errno == ENOENT);
> + FAIL_UNSUPPORTED ("/proc/%ld/setgroups not found\n", child_pid);
> + }
> +
> + xwrite (fd, str, str_len);
> + xclose(fd);
> +}
> +
> +static char child_stack[1024 * 1024];
> +
> +int
> +do_test (void)
> +{
> + base = support_create_and_chdir_toolong_temp_directory (BASENAME);
> +
> + xmkdir (MOUNT_NAME, S_IRWXU);
> + atexit (do_cleanup);
> +
> + TEST_VERIFY_EXIT (socketpair (AF_UNIX, SOCK_STREAM, 0, sockfd) == 0);
> + pid_t child_pid = xclone (child_func, NULL, child_stack,
> + sizeof (child_stack),
> + CLONE_NEWUSER | CLONE_NEWNS | SIGCHLD);
> +
> + xclose (sockfd[1]);
> + const int sock = sockfd[0];
> +
> + char map_path[64], map_buf[64];
Same comment as for setgroups_path.
> + snprintf (map_path, sizeof (map_path), ,
> + (long) child_pid);
> + snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getuid());
> + update_map (map_buf, map_path);
> +
> + proc_setgroups_write ((long) child_pid, "deny");
> + snprintf (map_path, sizeof (map_path), "/proc/%ld/gid_map",
> + (long) child_pid);
> + snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getgid());
> + update_map (map_buf, map_path);
> +
> + TEST_VERIFY_EXIT (send (sock, "1", 1, MSG_NOSIGNAL) == 1);
> + const int fd = recv_fd (sock);
> + TEST_VERIFY_EXIT (fd >= 0);
> + TEST_VERIFY_EXIT (fchdir (fd) == 0);
> +
> + static char buf[2 * 10 + 1];
> + memset (buf, 'A', sizeof(buf));
Space before (.
> +
> + /* Finally, call getcwd and check if it resulted in a buffer underflow. */
> + char * cwd = getcwd (buf + sizeof(buf) / 2, 1);
> + TEST_VERIFY (cwd == NULL);
> + TEST_VERIFY (errno == ERANGE);
> +
> + for (int i = 0; i < sizeof (buf); i++)
> + if (buf[i] != 'A')
> + {
> + printf ("buf[%d] = %02x\n", i, (unsigned int) buf[i]);
> + support_record_failure ();
> + }
> +
> + TEST_VERIFY_EXIT (send (sock, "a", 1, MSG_NOSIGNAL) == 1);
> + xclose (sock);
> + TEST_VERIFY_EXIT (xwaitpid (child_pid, NULL, 0) == child_pid);
> +
> + return 0;
> +}
> +
> +#define CLEANUP_HANDLER do_cleanup
> +#include <support/test-driver.c>
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v3 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999)
2022-01-21 16:41 ` Adhemerval Zanella
@ 2022-01-21 17:26 ` Siddhesh Poyarekar
2022-01-21 17:31 ` Adhemerval Zanella
2022-01-21 17:38 ` [PATCH v4] " Siddhesh Poyarekar
2022-01-21 18:04 ` [PATCH v5] " Siddhesh Poyarekar
2 siblings, 1 reply; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-21 17:26 UTC (permalink / raw)
To: Adhemerval Zanella, libc-alpha; +Cc: eggert, fweimer, Qualys Security Advisory
On 21/01/2022 22:11, Adhemerval Zanella wrote:
>
>
> On 20/01/2022 06:32, Siddhesh Poyarekar wrote:
>> No valid path returned by getcwd would fit into 1 byte, so reject the
>> size early and return NULL with errno set to ERANGE. This change is
>> prompted by CVE-2021-3999, which describes a single byte buffer
>> underflow and overflow when all of the following conditions are met:
>>
>> - The buffer size (i.e. the second argument of getcwd) is 1 byte
>> - The current working directory is too long
>> - '/' is also mounted on the current working directory
>>
>> Sequence of events:
>>
>> - In sysdeps/unix/sysv/linux/getcwd.c, the syscall returns ENAMETOOLONG
>> because the linux kernel checks for name length before it checks
>> buffer size
>>
>> - The code falls back to the generic getcwd in sysdeps/posix
>>
>> - In the generic func, the buf[0] is set to '\0' on line 250
>>
>> - this while loop on line 262 is bypassed:
>>
>> while (!(thisdev == rootdev && thisino == rootino))
>>
>> since the rootfs (/) is bind mounted onto the directory and the flow
>> goes on to line 449, where it puts a '/' in the byte before the
>> buffer.
>>
>> - Finally on line 458, it moves 2 bytes (the underflowed byte and the
>> '\0') to the buf[0] and buf[1], resulting in a 1 byte buffer overflow.
>>
>> - buf is returned on line 469 and errno is not set.
>>
>> This resolves BZ #28769.
>>
>> Signed-off-by: Qualys Security Advisory <qsa@qualys.com>
>> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
>
> Look good with just two fixed below for CMSG_DATA and a couple of comments.
> Ok with the fixes, the comments would be good but it is a blocker.
>
> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
>
>> ---
>> NEWS | 6 +
>> sysdeps/posix/getcwd.c | 7 +
>> sysdeps/unix/sysv/linux/Makefile | 7 +-
>> .../unix/sysv/linux/tst-getcwd-smallbuff.c | 245 ++++++++++++++++++
>> 4 files changed, 264 insertions(+), 1 deletion(-)
>> create mode 100644 sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
>>
>> diff --git a/NEWS b/NEWS
>> index 4c392a445e..07e9eac52d 100644
>> --- a/NEWS
>> +++ b/NEWS
>> @@ -170,6 +170,12 @@ Security related changes:
>> function could result in a memory leak and potential access of
>> uninitialized memory. Reported by Qualys.
>>
>> + CVE-2021-3999: Passing a buffer of size exactly 1 byte to the getcwd
>> + function may result in an off-by-one buffer underflow and overflow
>> + when the current working directory is longer than PATH_MAX and also
>> + corresponds to the / directory through an unprivileged mount
>> + namespace. Reported by Qualys.
>> +
>> The following bugs are resolved with this release:
>>
>> [The release manager will add the list generated by
>> diff --git a/sysdeps/posix/getcwd.c b/sysdeps/posix/getcwd.c
>> index e147a31a81..9d5787b6f4 100644
>> --- a/sysdeps/posix/getcwd.c
>> +++ b/sysdeps/posix/getcwd.c
>> @@ -187,6 +187,13 @@ __getcwd_generic (char *buf, size_t size)
>> size_t allocated = size;
>> size_t used;
>>
>> + /* A size of 1 byte is never useful. */
>> + if (allocated == 1)
>> + {
>> + __set_errno (ERANGE);
>> + return NULL;
>> + }
>> +
>> #if HAVE_MINIMALLY_WORKING_GETCWD
>> /* If AT_FDCWD is not defined, the algorithm below is O(N**2) and
>> this is much slower than the system getcwd (at least on
>> diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
>> index 85fc8cbf75..7ca9350c99 100644
>> --- a/sysdeps/unix/sysv/linux/Makefile
>> +++ b/sysdeps/unix/sysv/linux/Makefile
>> @@ -346,7 +346,12 @@ sysdep_routines += xstatconv internal_statvfs \
>>
>> sysdep_headers += bits/fcntl-linux.h
>>
>> -tests += tst-fallocate tst-fallocate64 tst-o_path-locks
>> +tests += \
>> + tst-fallocate \
>> + tst-fallocate64 \
>> + tst-getcwd-smallbuff \
>> + tst-o_path-locks \
>> +# tests
>> endif
>>
>> ifeq ($(subdir),elf)
>> diff --git a/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
>> new file mode 100644
>> index 0000000000..791dfe4d02
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
>> @@ -0,0 +1,245 @@
>> +/* Verify that getcwd returns ERANGE for size 1 byte and does not underflow
>> + buffer when the CWD is too long and is also a mount target of /. See bug
>> + #28769 or CVE-2021-3999 for more context.
>> + Copyright The GNU Toolchain Authors.
>> + This file is part of the GNU C Library.
>> +
>> + The GNU C Library is free software; you can redistribute it and/or
>> + modify it under the terms of the GNU Lesser General Public
>> + License as published by the Free Software Foundation; either
>> + version 2.1 of the License, or (at your option) any later version.
>> +
>> + The GNU C Library is distributed in the hope that it will be useful,
>> + but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
>> + Lesser General Public License for more details.
>> +
>> + You should have received a copy of the GNU Lesser General Public
>> + License along with the GNU C Library; if not, see
>> + <https://www.gnu.org/licenses/>. */
>> +
>> +#include <errno.h>
>> +#include <fcntl.h>
>> +#include <limits.h>
>> +#include <stdio.h>
>> +#include <stdlib.h>
>> +#include <string.h>
>> +#include <sys/mount.h>
>> +#include <sys/stat.h>
>> +#include <sys/types.h>
>> +#include <sys/wait.h>
>> +
>> +#include <sys/socket.h>
>> +#include <sys/un.h>
>> +#include <support/check.h>
>> +#include <support/temp_file.h>
>> +#include <support/xsched.h>
>> +#include <support/xunistd.h>
>> +
>> +#ifndef PATH_MAX
>> +# define PATH_MAX 1024
>> +#endif
>
> No need since it is a Linux only test and PATH_MAX is always defined.
Ahh, I didn't actually need it anyway, leftover from a previous
iteration. I'll remove it.
>
>> +
>> +static char *base;
>> +#define BASENAME "tst-getcwd-smallbuff"
>> +#define MOUNT_NAME "mpoint"
>> +static int sockfd[2];
>> +
>> +static void
>> +do_cleanup (void)
>> +{
>> + support_chdir_toolong_temp_directory (base);
>> + TEST_VERIFY_EXIT (rmdir (MOUNT_NAME) == 0);
>> + free (base);
>> +}
>> +
>> +static void
>> +send_fd (const int sock, const int fd)
>> +{
>> + struct msghdr msg;
>> + union
>> + {
>> + struct cmsghdr hdr;
>> + char buf[CMSG_SPACE (sizeof (int))];
>> + } cmsgbuf;
>
> Maybe zero-initialize both first to avoid the memset below?
OK.
>
>> + struct cmsghdr *cmsg;
>> + struct iovec vec;
>> + char ch = 'A';
>> + ssize_t n;
>> +
>> + memset (&msg, 0, sizeof (msg));
>> + memset (&cmsgbuf, 0, sizeof (cmsgbuf));
>> + msg.msg_control = &cmsgbuf.buf;
>> + msg.msg_controllen = sizeof (cmsgbuf.buf);
>> +
>> + cmsg = CMSG_FIRSTHDR (&msg);
>> + cmsg->cmsg_len = CMSG_LEN (sizeof (int));
>> + cmsg->cmsg_level = SOL_SOCKET;
>> + cmsg->cmsg_type = SCM_RIGHTS;
>> + *(int *) CMSG_DATA (cmsg) = fd;
>
> I think CMSG_DATA does not guarantee the alignment, so I think it would be
> safe to use memcpy here:
>
> memcpy (CMSG_DATA (cmsg), &fd, sizeof (fd));
OK.
>
>> +
>> + vec.iov_base = &ch;
>> + vec.iov_len = 1;
>> + msg.msg_iov = &vec;
>> + msg.msg_iovlen = 1;
>> +
>> + while ((n = sendmsg (sock, &msg, 0)) == -1 && errno == EINTR);
>> +
>> + TEST_VERIFY_EXIT (n == 1);
>> +}
>> +
>
> Ok.
>
>> +static int
>> +recv_fd (const int sock)
>> +{
>> + struct msghdr msg;
>
> Maybe also zero-initialize here.
>
>> + union
>> + {
>> + struct cmsghdr hdr;
>> + char buf[CMSG_SPACE(sizeof(int))];
>> + } cmsgbuf;
>> + struct cmsghdr *cmsg;
>> + struct iovec vec;
>> + ssize_t n;
>> + char ch = '\0';
>> + int fd = -1;
>> +
>> + memset (&msg, 0, sizeof (msg));
>> + vec.iov_base = &ch;
>> + vec.iov_len = 1;
>> + msg.msg_iov = &vec;
>> + msg.msg_iovlen = 1;
>> +
>> + memset (&cmsgbuf, 0, sizeof (cmsgbuf));
>> + msg.msg_control = &cmsgbuf.buf;
>> + msg.msg_controllen = sizeof (cmsgbuf.buf);
>> +
>> + while ((n = recvmsg (sock, &msg, 0)) == -1 && errno == EINTR);
>> + if (n != 1 || ch != 'A')
>> + return -1;
>> +
>> + cmsg = CMSG_FIRSTHDR (&msg);
>> + if (cmsg == NULL)
>> + return -1;
>> + if (cmsg->cmsg_type != SCM_RIGHTS)
>> + return -1;
>> + fd = *(const int *) CMSG_DATA (cmsg);
>
> Same as before, I think you will need to copy to a temporary using memcpy.
Why not just:
memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
i.e., is a temporary necessary?
>
>> + if (fd < 0)
>> + return -1;
>> + return fd;
>> +}
>> +
>> +static int
>> +child_func (void * const arg)
>> +{
>> + xclose (sockfd[0]);
>> + const int sock = sockfd[1];
>> + char ch;
>> +
>> + TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
>> + TEST_VERIFY_EXIT (ch == '1');
>> +
>> + if (mount ("/", MOUNT_NAME, NULL, MS_BIND | MS_REC, NULL))
>> + FAIL_EXIT1 ("mount failed: %m\n");
>> + const int fd = xopen ("mpoint",
>> + O_RDONLY | O_PATH | O_DIRECTORY | O_NOFOLLOW, 0);
>> +
>> + send_fd (sock, fd);
>> + xclose (fd);
>> +
>> + TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
>> + TEST_VERIFY_EXIT (ch == 'a');
>> +
>> + xclose (sock);
>> + return 0;
>> +}
>> +
>> +static void
>> +update_map (char * const mapping, const char * const map_file)
>> +{
>> + const size_t map_len = strlen (mapping);
>> +
>> + const int fd = xopen (map_file, O_WRONLY, 0);
>> + xwrite (fd, mapping, map_len);
>> + xclose (fd);
>> +}
>> +
>> +static void
>> +proc_setgroups_write (const long child_pid, const char * const str)
>> +{
>> + const size_t str_len = strlen(str);
>> +
>> + char setgroups_path[64];
>
>
> Maybe define the size as:
>
> /* The path is the form /proc/%ld/setgroups. */
> char map_path[sizeof("/proc/setgroups") + INT_STRLEN_BOUND (long int)];
>
OK.
>> + snprintf (setgroups_path, sizeof (setgroups_path),
>> + "/proc/%ld/setgroups", child_pid);
>> +
>> + const int fd = open (setgroups_path, O_WRONLY);
>> +
>> + if (fd < 0)
>> + {
>> + TEST_VERIFY_EXIT (errno == ENOENT);
>> + FAIL_UNSUPPORTED ("/proc/%ld/setgroups not found\n", child_pid);
>> + }
>> +
>> + xwrite (fd, str, str_len);
>> + xclose(fd);
>> +}
>> +
>> +static char child_stack[1024 * 1024];
>> +
>> +int
>> +do_test (void)
>> +{
>> + base = support_create_and_chdir_toolong_temp_directory (BASENAME);
>> +
>> + xmkdir (MOUNT_NAME, S_IRWXU);
>> + atexit (do_cleanup);
>> +
>> + TEST_VERIFY_EXIT (socketpair (AF_UNIX, SOCK_STREAM, 0, sockfd) == 0);
>> + pid_t child_pid = xclone (child_func, NULL, child_stack,
>> + sizeof (child_stack),
>> + CLONE_NEWUSER | CLONE_NEWNS | SIGCHLD);
>> +
>> + xclose (sockfd[1]);
>> + const int sock = sockfd[0];
>> +
>> + char map_path[64], map_buf[64];
>
> Same comment as for setgroups_path.
>
>> + snprintf (map_path, sizeof (map_path), ,
>> + (long) child_pid);
>> + snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getuid());
>> + update_map (map_buf, map_path);
>> +
>> + proc_setgroups_write ((long) child_pid, "deny");
>> + snprintf (map_path, sizeof (map_path), "/proc/%ld/gid_map",
>> + (long) child_pid);
>> + snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getgid());
>> + update_map (map_buf, map_path);
>> +
>> + TEST_VERIFY_EXIT (send (sock, "1", 1, MSG_NOSIGNAL) == 1);
>> + const int fd = recv_fd (sock);
>> + TEST_VERIFY_EXIT (fd >= 0);
>> + TEST_VERIFY_EXIT (fchdir (fd) == 0);
>> +
>> + static char buf[2 * 10 + 1];
>> + memset (buf, 'A', sizeof(buf));
>
>
> Space before (.
>
>> +
>> + /* Finally, call getcwd and check if it resulted in a buffer underflow. */
>> + char * cwd = getcwd (buf + sizeof(buf) / 2, 1);
>> + TEST_VERIFY (cwd == NULL);
>> + TEST_VERIFY (errno == ERANGE);
>> +
>> + for (int i = 0; i < sizeof (buf); i++)
>> + if (buf[i] != 'A')
>> + {
>> + printf ("buf[%d] = %02x\n", i, (unsigned int) buf[i]);
>> + support_record_failure ();
>> + }
>> +
>> + TEST_VERIFY_EXIT (send (sock, "a", 1, MSG_NOSIGNAL) == 1);
>> + xclose (sock);
>> + TEST_VERIFY_EXIT (xwaitpid (child_pid, NULL, 0) == child_pid);
>> +
>> + return 0;
>> +}
>> +
>> +#define CLEANUP_HANDLER do_cleanup
>> +#include <support/test-driver.c>
>
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v3 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999)
2022-01-21 17:26 ` Siddhesh Poyarekar
@ 2022-01-21 17:31 ` Adhemerval Zanella
0 siblings, 0 replies; 36+ messages in thread
From: Adhemerval Zanella @ 2022-01-21 17:31 UTC (permalink / raw)
To: Siddhesh Poyarekar, libc-alpha; +Cc: eggert, fweimer, Qualys Security Advisory
On 21/01/2022 14:26, Siddhesh Poyarekar wrote:
> On 21/01/2022 22:11, Adhemerval Zanella wrote:
>>
>>
>> On 20/01/2022 06:32, Siddhesh Poyarekar wrote:
>>> + cmsg = CMSG_FIRSTHDR (&msg);
>>> + if (cmsg == NULL)
>>> + return -1;
>>> + if (cmsg->cmsg_type != SCM_RIGHTS)
>>> + return -1;
>>> + fd = *(const int *) CMSG_DATA (cmsg);
>>
>> Same as before, I think you will need to copy to a temporary using memcpy.
>
> Why not just:
>
> memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
>
> i.e., is a temporary necessary?
Not really, the above works just fine.
^ permalink raw reply [flat|nested] 36+ messages in thread
* [PATCH v4] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999)
2022-01-21 16:41 ` Adhemerval Zanella
2022-01-21 17:26 ` Siddhesh Poyarekar
@ 2022-01-21 17:38 ` Siddhesh Poyarekar
2022-01-21 17:59 ` Andreas Schwab
2022-01-21 18:04 ` [PATCH v5] " Siddhesh Poyarekar
2 siblings, 1 reply; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-21 17:38 UTC (permalink / raw)
To: libc-alpha; +Cc: Adhemerval Zanella, Qualys Security Advisory
Fixed up, I'll push this if there are no further issues.
Thanks,
Siddhesh
-->8--
No valid path returned by getcwd would fit into 1 byte, so reject the
size early and return NULL with errno set to ERANGE. This change is
prompted by CVE-2021-3999, which describes a single byte buffer
underflow and overflow when all of the following conditions are met:
- The buffer size (i.e. the second argument of getcwd) is 1 byte
- The current working directory is too long
- '/' is also mounted on the current working directory
Sequence of events:
- In sysdeps/unix/sysv/linux/getcwd.c, the syscall returns ENAMETOOLONG
because the linux kernel checks for name length before it checks
buffer size
- The code falls back to the generic getcwd in sysdeps/posix
- In the generic func, the buf[0] is set to '\0' on line 250
- this while loop on line 262 is bypassed:
while (!(thisdev == rootdev && thisino == rootino))
since the rootfs (/) is bind mounted onto the directory and the flow
goes on to line 449, where it puts a '/' in the byte before the
buffer.
- Finally on line 458, it moves 2 bytes (the underflowed byte and the
'\0') to the buf[0] and buf[1], resulting in a 1 byte buffer overflow.
- buf is returned on line 469 and errno is not set.
This resolves BZ #28769.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Signed-off-by: Qualys Security Advisory <qsa@qualys.com>
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
NEWS | 6 +
sysdeps/posix/getcwd.c | 7 +
sysdeps/unix/sysv/linux/Makefile | 7 +-
.../unix/sysv/linux/tst-getcwd-smallbuff.c | 243 ++++++++++++++++++
4 files changed, 262 insertions(+), 1 deletion(-)
create mode 100644 sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
diff --git a/NEWS b/NEWS
index 4c392a445e..07e9eac52d 100644
--- a/NEWS
+++ b/NEWS
@@ -170,6 +170,12 @@ Security related changes:
function could result in a memory leak and potential access of
uninitialized memory. Reported by Qualys.
+ CVE-2021-3999: Passing a buffer of size exactly 1 byte to the getcwd
+ function may result in an off-by-one buffer underflow and overflow
+ when the current working directory is longer than PATH_MAX and also
+ corresponds to the / directory through an unprivileged mount
+ namespace. Reported by Qualys.
+
The following bugs are resolved with this release:
[The release manager will add the list generated by
diff --git a/sysdeps/posix/getcwd.c b/sysdeps/posix/getcwd.c
index e147a31a81..9d5787b6f4 100644
--- a/sysdeps/posix/getcwd.c
+++ b/sysdeps/posix/getcwd.c
@@ -187,6 +187,13 @@ __getcwd_generic (char *buf, size_t size)
size_t allocated = size;
size_t used;
+ /* A size of 1 byte is never useful. */
+ if (allocated == 1)
+ {
+ __set_errno (ERANGE);
+ return NULL;
+ }
+
#if HAVE_MINIMALLY_WORKING_GETCWD
/* If AT_FDCWD is not defined, the algorithm below is O(N**2) and
this is much slower than the system getcwd (at least on
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 85fc8cbf75..7ca9350c99 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -346,7 +346,12 @@ sysdep_routines += xstatconv internal_statvfs \
sysdep_headers += bits/fcntl-linux.h
-tests += tst-fallocate tst-fallocate64 tst-o_path-locks
+tests += \
+ tst-fallocate \
+ tst-fallocate64 \
+ tst-getcwd-smallbuff \
+ tst-o_path-locks \
+# tests
endif
ifeq ($(subdir),elf)
diff --git a/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
new file mode 100644
index 0000000000..212f9b94f3
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
@@ -0,0 +1,243 @@
+/* Verify that getcwd returns ERANGE for size 1 byte and does not underflow
+ buffer when the CWD is too long and is also a mount target of /. See bug
+ #28769 or CVE-2021-3999 for more context.
+ Copyright The GNU Toolchain Authors.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <intprops.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <support/check.h>
+#include <support/temp_file.h>
+#include <support/xsched.h>
+#include <support/xunistd.h>
+
+static char *base;
+#define BASENAME "tst-getcwd-smallbuff"
+#define MOUNT_NAME "mpoint"
+static int sockfd[2];
+
+static void
+do_cleanup (void)
+{
+ support_chdir_toolong_temp_directory (base);
+ TEST_VERIFY_EXIT (rmdir (MOUNT_NAME) == 0);
+ free (base);
+}
+
+static void
+send_fd (const int sock, const int fd)
+{
+ struct msghdr msg = {0};
+ union
+ {
+ struct cmsghdr hdr;
+ char buf[CMSG_SPACE (sizeof (int))];
+ } cmsgbuf = {0};
+ struct cmsghdr *cmsg;
+ struct iovec vec;
+ char ch = 'A';
+ ssize_t n;
+
+ msg.msg_control = &cmsgbuf.buf;
+ msg.msg_controllen = sizeof (cmsgbuf.buf);
+
+ cmsg = CMSG_FIRSTHDR (&msg);
+ cmsg->cmsg_len = CMSG_LEN (sizeof (int));
+ cmsg->cmsg_level = SOL_SOCKET;
+ cmsg->cmsg_type = SCM_RIGHTS;
+ memcpy (CMSG_DATA (cmsg), &fd, sizeof (fd));
+
+ vec.iov_base = &ch;
+ vec.iov_len = 1;
+ msg.msg_iov = &vec;
+ msg.msg_iovlen = 1;
+
+ while ((n = sendmsg (sock, &msg, 0)) == -1 && errno == EINTR);
+
+ TEST_VERIFY_EXIT (n == 1);
+}
+
+static int
+recv_fd (const int sock)
+{
+ struct msghdr msg;
+ union
+ {
+ struct cmsghdr hdr;
+ char buf[CMSG_SPACE(sizeof(int))];
+ } cmsgbuf;
+ struct cmsghdr *cmsg;
+ struct iovec vec;
+ ssize_t n;
+ char ch = '\0';
+ int fd = -1;
+
+ memset (&msg, 0, sizeof (msg));
+ vec.iov_base = &ch;
+ vec.iov_len = 1;
+ msg.msg_iov = &vec;
+ msg.msg_iovlen = 1;
+
+ memset (&cmsgbuf, 0, sizeof (cmsgbuf));
+ msg.msg_control = &cmsgbuf.buf;
+ msg.msg_controllen = sizeof (cmsgbuf.buf);
+
+ while ((n = recvmsg (sock, &msg, 0)) == -1 && errno == EINTR);
+ if (n != 1 || ch != 'A')
+ return -1;
+
+ cmsg = CMSG_FIRSTHDR (&msg);
+ if (cmsg == NULL)
+ return -1;
+ if (cmsg->cmsg_type != SCM_RIGHTS)
+ return -1;
+ memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
+ if (fd < 0)
+ return -1;
+ return fd;
+}
+
+static int
+child_func (void * const arg)
+{
+ xclose (sockfd[0]);
+ const int sock = sockfd[1];
+ char ch;
+
+ TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
+ TEST_VERIFY_EXIT (ch == '1');
+
+ if (mount ("/", MOUNT_NAME, NULL, MS_BIND | MS_REC, NULL))
+ FAIL_EXIT1 ("mount failed: %m\n");
+ const int fd = xopen ("mpoint",
+ O_RDONLY | O_PATH | O_DIRECTORY | O_NOFOLLOW, 0);
+
+ send_fd (sock, fd);
+ xclose (fd);
+
+ TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
+ TEST_VERIFY_EXIT (ch == 'a');
+
+ xclose (sock);
+ return 0;
+}
+
+static void
+update_map (char * const mapping, const char * const map_file)
+{
+ const size_t map_len = strlen (mapping);
+
+ const int fd = xopen (map_file, O_WRONLY, 0);
+ xwrite (fd, mapping, map_len);
+ xclose (fd);
+}
+
+static void
+proc_setgroups_write (const long child_pid, const char * const str)
+{
+ const size_t str_len = strlen(str);
+
+ char setgroups_path[sizeof ("/proc//setgroups") + INT_STRLEN_BOUND (long)];
+
+ snprintf (setgroups_path, sizeof (setgroups_path),
+ "/proc/%ld/setgroups", child_pid);
+
+ const int fd = open (setgroups_path, O_WRONLY);
+
+ if (fd < 0)
+ {
+ TEST_VERIFY_EXIT (errno == ENOENT);
+ FAIL_UNSUPPORTED ("/proc/%ld/setgroups not found\n", child_pid);
+ }
+
+ xwrite (fd, str, str_len);
+ xclose(fd);
+}
+
+static char child_stack[1024 * 1024];
+
+int
+do_test (void)
+{
+ base = support_create_and_chdir_toolong_temp_directory (BASENAME);
+
+ xmkdir (MOUNT_NAME, S_IRWXU);
+ atexit (do_cleanup);
+
+ TEST_VERIFY_EXIT (socketpair (AF_UNIX, SOCK_STREAM, 0, sockfd) == 0);
+ pid_t child_pid = xclone (child_func, NULL, child_stack,
+ sizeof (child_stack),
+ CLONE_NEWUSER | CLONE_NEWNS | SIGCHLD);
+
+ xclose (sockfd[1]);
+ const int sock = sockfd[0];
+
+ char map_path[sizeof ("/proc//uid_map") + INT_STRLEN_BOUND (long)];
+ char map_buf[sizeof ("0 1") + INT_STRLEN_BOUND (long)];
+
+ snprintf (map_path, sizeof (map_path), "/proc/%ld/uid_map",
+ (long) child_pid);
+ snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getuid());
+ update_map (map_buf, map_path);
+
+ proc_setgroups_write ((long) child_pid, "deny");
+ snprintf (map_path, sizeof (map_path), "/proc/%ld/gid_map",
+ (long) child_pid);
+ snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getgid());
+ update_map (map_buf, map_path);
+
+ TEST_VERIFY_EXIT (send (sock, "1", 1, MSG_NOSIGNAL) == 1);
+ const int fd = recv_fd (sock);
+ TEST_VERIFY_EXIT (fd >= 0);
+ TEST_VERIFY_EXIT (fchdir (fd) == 0);
+
+ static char buf[2 * 10 + 1];
+ memset (buf, 'A', sizeof (buf));
+
+ /* Finally, call getcwd and check if it resulted in a buffer underflow. */
+ char * cwd = getcwd (buf + sizeof (buf) / 2, 1);
+ TEST_VERIFY (cwd == NULL);
+ TEST_VERIFY (errno == ERANGE);
+
+ for (int i = 0; i < sizeof (buf); i++)
+ if (buf[i] != 'A')
+ {
+ printf ("buf[%d] = %02x\n", i, (unsigned int) buf[i]);
+ support_record_failure ();
+ }
+
+ TEST_VERIFY_EXIT (send (sock, "a", 1, MSG_NOSIGNAL) == 1);
+ xclose (sock);
+ TEST_VERIFY_EXIT (xwaitpid (child_pid, NULL, 0) == child_pid);
+
+ return 0;
+}
+
+#define CLEANUP_HANDLER do_cleanup
+#include <support/test-driver.c>
--
2.34.1
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v4] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999)
2022-01-21 17:38 ` [PATCH v4] " Siddhesh Poyarekar
@ 2022-01-21 17:59 ` Andreas Schwab
2022-01-21 18:02 ` Siddhesh Poyarekar
0 siblings, 1 reply; 36+ messages in thread
From: Andreas Schwab @ 2022-01-21 17:59 UTC (permalink / raw)
To: Siddhesh Poyarekar via Libc-alpha
Cc: Siddhesh Poyarekar, Qualys Security Advisory
On Jan 21 2022, Siddhesh Poyarekar via Libc-alpha wrote:
> +static int
> +recv_fd (const int sock)
> +{
> + struct msghdr msg;
> + union
> + {
> + struct cmsghdr hdr;
> + char buf[CMSG_SPACE(sizeof(int))];
> + } cmsgbuf;
Zero-init like in send_fd.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v4] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999)
2022-01-21 17:59 ` Andreas Schwab
@ 2022-01-21 18:02 ` Siddhesh Poyarekar
0 siblings, 0 replies; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-21 18:02 UTC (permalink / raw)
To: Andreas Schwab, Siddhesh Poyarekar via Libc-alpha
Cc: Qualys Security Advisory
On 21/01/2022 23:29, Andreas Schwab wrote:
> On Jan 21 2022, Siddhesh Poyarekar via Libc-alpha wrote:
>
>> +static int
>> +recv_fd (const int sock)
>> +{
>> + struct msghdr msg;
>> + union
>> + {
>> + struct cmsghdr hdr;
>> + char buf[CMSG_SPACE(sizeof(int))];
>> + } cmsgbuf;
>
> Zero-init like in send_fd.
>
Thanks, I missed that. Sending v5.
Siddhesh
^ permalink raw reply [flat|nested] 36+ messages in thread
* [PATCH v5] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999)
2022-01-21 16:41 ` Adhemerval Zanella
2022-01-21 17:26 ` Siddhesh Poyarekar
2022-01-21 17:38 ` [PATCH v4] " Siddhesh Poyarekar
@ 2022-01-21 18:04 ` Siddhesh Poyarekar
2022-01-24 6:03 ` Siddhesh Poyarekar
2 siblings, 1 reply; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-21 18:04 UTC (permalink / raw)
To: libc-alpha; +Cc: Andreas Schwab, Adhemerval Zanella, Qualys Security Advisory
No valid path returned by getcwd would fit into 1 byte, so reject the
size early and return NULL with errno set to ERANGE. This change is
prompted by CVE-2021-3999, which describes a single byte buffer
underflow and overflow when all of the following conditions are met:
- The buffer size (i.e. the second argument of getcwd) is 1 byte
- The current working directory is too long
- '/' is also mounted on the current working directory
Sequence of events:
- In sysdeps/unix/sysv/linux/getcwd.c, the syscall returns ENAMETOOLONG
because the linux kernel checks for name length before it checks
buffer size
- The code falls back to the generic getcwd in sysdeps/posix
- In the generic func, the buf[0] is set to '\0' on line 250
- this while loop on line 262 is bypassed:
while (!(thisdev == rootdev && thisino == rootino))
since the rootfs (/) is bind mounted onto the directory and the flow
goes on to line 449, where it puts a '/' in the byte before the
buffer.
- Finally on line 458, it moves 2 bytes (the underflowed byte and the
'\0') to the buf[0] and buf[1], resulting in a 1 byte buffer overflow.
- buf is returned on line 469 and errno is not set.
This resolves BZ #28769.
Reviewed-by: Andreas Schwab <schwab@linux-m68k.org>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Signed-off-by: Qualys Security Advisory <qsa@qualys.com>
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
NEWS | 6 +
sysdeps/posix/getcwd.c | 7 +
sysdeps/unix/sysv/linux/Makefile | 7 +-
.../unix/sysv/linux/tst-getcwd-smallbuff.c | 241 ++++++++++++++++++
4 files changed, 260 insertions(+), 1 deletion(-)
create mode 100644 sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
diff --git a/NEWS b/NEWS
index 4c392a445e..07e9eac52d 100644
--- a/NEWS
+++ b/NEWS
@@ -170,6 +170,12 @@ Security related changes:
function could result in a memory leak and potential access of
uninitialized memory. Reported by Qualys.
+ CVE-2021-3999: Passing a buffer of size exactly 1 byte to the getcwd
+ function may result in an off-by-one buffer underflow and overflow
+ when the current working directory is longer than PATH_MAX and also
+ corresponds to the / directory through an unprivileged mount
+ namespace. Reported by Qualys.
+
The following bugs are resolved with this release:
[The release manager will add the list generated by
diff --git a/sysdeps/posix/getcwd.c b/sysdeps/posix/getcwd.c
index e147a31a81..9d5787b6f4 100644
--- a/sysdeps/posix/getcwd.c
+++ b/sysdeps/posix/getcwd.c
@@ -187,6 +187,13 @@ __getcwd_generic (char *buf, size_t size)
size_t allocated = size;
size_t used;
+ /* A size of 1 byte is never useful. */
+ if (allocated == 1)
+ {
+ __set_errno (ERANGE);
+ return NULL;
+ }
+
#if HAVE_MINIMALLY_WORKING_GETCWD
/* If AT_FDCWD is not defined, the algorithm below is O(N**2) and
this is much slower than the system getcwd (at least on
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index 85fc8cbf75..7ca9350c99 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -346,7 +346,12 @@ sysdep_routines += xstatconv internal_statvfs \
sysdep_headers += bits/fcntl-linux.h
-tests += tst-fallocate tst-fallocate64 tst-o_path-locks
+tests += \
+ tst-fallocate \
+ tst-fallocate64 \
+ tst-getcwd-smallbuff \
+ tst-o_path-locks \
+# tests
endif
ifeq ($(subdir),elf)
diff --git a/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
new file mode 100644
index 0000000000..d460d6e766
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
@@ -0,0 +1,241 @@
+/* Verify that getcwd returns ERANGE for size 1 byte and does not underflow
+ buffer when the CWD is too long and is also a mount target of /. See bug
+ #28769 or CVE-2021-3999 for more context.
+ Copyright The GNU Toolchain Authors.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <intprops.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <support/check.h>
+#include <support/temp_file.h>
+#include <support/xsched.h>
+#include <support/xunistd.h>
+
+static char *base;
+#define BASENAME "tst-getcwd-smallbuff"
+#define MOUNT_NAME "mpoint"
+static int sockfd[2];
+
+static void
+do_cleanup (void)
+{
+ support_chdir_toolong_temp_directory (base);
+ TEST_VERIFY_EXIT (rmdir (MOUNT_NAME) == 0);
+ free (base);
+}
+
+static void
+send_fd (const int sock, const int fd)
+{
+ struct msghdr msg = {0};
+ union
+ {
+ struct cmsghdr hdr;
+ char buf[CMSG_SPACE (sizeof (int))];
+ } cmsgbuf = {0};
+ struct cmsghdr *cmsg;
+ struct iovec vec;
+ char ch = 'A';
+ ssize_t n;
+
+ msg.msg_control = &cmsgbuf.buf;
+ msg.msg_controllen = sizeof (cmsgbuf.buf);
+
+ cmsg = CMSG_FIRSTHDR (&msg);
+ cmsg->cmsg_len = CMSG_LEN (sizeof (int));
+ cmsg->cmsg_level = SOL_SOCKET;
+ cmsg->cmsg_type = SCM_RIGHTS;
+ memcpy (CMSG_DATA (cmsg), &fd, sizeof (fd));
+
+ vec.iov_base = &ch;
+ vec.iov_len = 1;
+ msg.msg_iov = &vec;
+ msg.msg_iovlen = 1;
+
+ while ((n = sendmsg (sock, &msg, 0)) == -1 && errno == EINTR);
+
+ TEST_VERIFY_EXIT (n == 1);
+}
+
+static int
+recv_fd (const int sock)
+{
+ struct msghdr msg = {0};
+ union
+ {
+ struct cmsghdr hdr;
+ char buf[CMSG_SPACE(sizeof(int))];
+ } cmsgbuf = {0};
+ struct cmsghdr *cmsg;
+ struct iovec vec;
+ ssize_t n;
+ char ch = '\0';
+ int fd = -1;
+
+ vec.iov_base = &ch;
+ vec.iov_len = 1;
+ msg.msg_iov = &vec;
+ msg.msg_iovlen = 1;
+
+ msg.msg_control = &cmsgbuf.buf;
+ msg.msg_controllen = sizeof (cmsgbuf.buf);
+
+ while ((n = recvmsg (sock, &msg, 0)) == -1 && errno == EINTR);
+ if (n != 1 || ch != 'A')
+ return -1;
+
+ cmsg = CMSG_FIRSTHDR (&msg);
+ if (cmsg == NULL)
+ return -1;
+ if (cmsg->cmsg_type != SCM_RIGHTS)
+ return -1;
+ memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
+ if (fd < 0)
+ return -1;
+ return fd;
+}
+
+static int
+child_func (void * const arg)
+{
+ xclose (sockfd[0]);
+ const int sock = sockfd[1];
+ char ch;
+
+ TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
+ TEST_VERIFY_EXIT (ch == '1');
+
+ if (mount ("/", MOUNT_NAME, NULL, MS_BIND | MS_REC, NULL))
+ FAIL_EXIT1 ("mount failed: %m\n");
+ const int fd = xopen ("mpoint",
+ O_RDONLY | O_PATH | O_DIRECTORY | O_NOFOLLOW, 0);
+
+ send_fd (sock, fd);
+ xclose (fd);
+
+ TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
+ TEST_VERIFY_EXIT (ch == 'a');
+
+ xclose (sock);
+ return 0;
+}
+
+static void
+update_map (char * const mapping, const char * const map_file)
+{
+ const size_t map_len = strlen (mapping);
+
+ const int fd = xopen (map_file, O_WRONLY, 0);
+ xwrite (fd, mapping, map_len);
+ xclose (fd);
+}
+
+static void
+proc_setgroups_write (const long child_pid, const char * const str)
+{
+ const size_t str_len = strlen(str);
+
+ char setgroups_path[sizeof ("/proc//setgroups") + INT_STRLEN_BOUND (long)];
+
+ snprintf (setgroups_path, sizeof (setgroups_path),
+ "/proc/%ld/setgroups", child_pid);
+
+ const int fd = open (setgroups_path, O_WRONLY);
+
+ if (fd < 0)
+ {
+ TEST_VERIFY_EXIT (errno == ENOENT);
+ FAIL_UNSUPPORTED ("/proc/%ld/setgroups not found\n", child_pid);
+ }
+
+ xwrite (fd, str, str_len);
+ xclose(fd);
+}
+
+static char child_stack[1024 * 1024];
+
+int
+do_test (void)
+{
+ base = support_create_and_chdir_toolong_temp_directory (BASENAME);
+
+ xmkdir (MOUNT_NAME, S_IRWXU);
+ atexit (do_cleanup);
+
+ TEST_VERIFY_EXIT (socketpair (AF_UNIX, SOCK_STREAM, 0, sockfd) == 0);
+ pid_t child_pid = xclone (child_func, NULL, child_stack,
+ sizeof (child_stack),
+ CLONE_NEWUSER | CLONE_NEWNS | SIGCHLD);
+
+ xclose (sockfd[1]);
+ const int sock = sockfd[0];
+
+ char map_path[sizeof ("/proc//uid_map") + INT_STRLEN_BOUND (long)];
+ char map_buf[sizeof ("0 1") + INT_STRLEN_BOUND (long)];
+
+ snprintf (map_path, sizeof (map_path), "/proc/%ld/uid_map",
+ (long) child_pid);
+ snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getuid());
+ update_map (map_buf, map_path);
+
+ proc_setgroups_write ((long) child_pid, "deny");
+ snprintf (map_path, sizeof (map_path), "/proc/%ld/gid_map",
+ (long) child_pid);
+ snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getgid());
+ update_map (map_buf, map_path);
+
+ TEST_VERIFY_EXIT (send (sock, "1", 1, MSG_NOSIGNAL) == 1);
+ const int fd = recv_fd (sock);
+ TEST_VERIFY_EXIT (fd >= 0);
+ TEST_VERIFY_EXIT (fchdir (fd) == 0);
+
+ static char buf[2 * 10 + 1];
+ memset (buf, 'A', sizeof (buf));
+
+ /* Finally, call getcwd and check if it resulted in a buffer underflow. */
+ char * cwd = getcwd (buf + sizeof (buf) / 2, 1);
+ TEST_VERIFY (cwd == NULL);
+ TEST_VERIFY (errno == ERANGE);
+
+ for (int i = 0; i < sizeof (buf); i++)
+ if (buf[i] != 'A')
+ {
+ printf ("buf[%d] = %02x\n", i, (unsigned int) buf[i]);
+ support_record_failure ();
+ }
+
+ TEST_VERIFY_EXIT (send (sock, "a", 1, MSG_NOSIGNAL) == 1);
+ xclose (sock);
+ TEST_VERIFY_EXIT (xwaitpid (child_pid, NULL, 0) == child_pid);
+
+ return 0;
+}
+
+#define CLEANUP_HANDLER do_cleanup
+#include <support/test-driver.c>
--
2.34.1
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770]
2022-01-20 9:32 ` [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770] Siddhesh Poyarekar
@ 2022-01-21 23:22 ` Joseph Myers
2022-01-22 3:47 ` Siddhesh Poyarekar
2022-01-22 14:45 ` [PATCH] tst-realpath-toolong: Fix hurd build Siddhesh Poyarekar
2022-01-24 13:45 ` [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770] Andreas Schwab
1 sibling, 2 replies; 36+ messages in thread
From: Joseph Myers @ 2022-01-21 23:22 UTC (permalink / raw)
To: Siddhesh Poyarekar; +Cc: libc-alpha, fweimer
On Thu, 20 Jan 2022, Siddhesh Poyarekar via Libc-alpha wrote:
> diff --git a/stdlib/tst-realpath-toolong.c b/stdlib/tst-realpath-toolong.c
> + char buf[PATH_MAX + 1];
This has broken the testsuite build for Hurd.
tst-realpath-toolong.c: In function 'do_test':
tst-realpath-toolong.c:37:12: error: 'PATH_MAX' undeclared (first use in this function)
--
Joseph S. Myers
joseph@codesourcery.com
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770]
2022-01-21 23:22 ` Joseph Myers
@ 2022-01-22 3:47 ` Siddhesh Poyarekar
2022-01-22 14:45 ` [PATCH] tst-realpath-toolong: Fix hurd build Siddhesh Poyarekar
1 sibling, 0 replies; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-22 3:47 UTC (permalink / raw)
To: Joseph Myers; +Cc: libc-alpha, fweimer
On 22/01/2022 04:52, Joseph Myers wrote:
> On Thu, 20 Jan 2022, Siddhesh Poyarekar via Libc-alpha wrote:
>
>> diff --git a/stdlib/tst-realpath-toolong.c b/stdlib/tst-realpath-toolong.c
>
>> + char buf[PATH_MAX + 1];
>
> This has broken the testsuite build for Hurd.
>
> tst-realpath-toolong.c: In function 'do_test':
> tst-realpath-toolong.c:37:12: error: 'PATH_MAX' undeclared (first use in this function)
>
Sorry I missed that, I'll post a fix. I was getting a different build
error on hurd which prevented me from seeing this. I'm rebuilding my
build-many-glibcs to see if that fixes it.
Thanks,
Siddhesh
^ permalink raw reply [flat|nested] 36+ messages in thread
* [PATCH] tst-realpath-toolong: Fix hurd build
2022-01-21 23:22 ` Joseph Myers
2022-01-22 3:47 ` Siddhesh Poyarekar
@ 2022-01-22 14:45 ` Siddhesh Poyarekar
2022-01-23 0:36 ` Samuel Thibault
1 sibling, 1 reply; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-22 14:45 UTC (permalink / raw)
To: libc-alpha; +Cc: joseph
We don't really need a bigger buffer for realpath since it should fail
and return NULL. In the bug too, the buffer itself is not accessed; it
is in fact left untouched. Drop the PATH_MAX use and pass a single char
address.
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
stdlib/tst-realpath-toolong.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/stdlib/tst-realpath-toolong.c b/stdlib/tst-realpath-toolong.c
index 8bed772460..ed84787a32 100644
--- a/stdlib/tst-realpath-toolong.c
+++ b/stdlib/tst-realpath-toolong.c
@@ -34,8 +34,8 @@ do_test (void)
{
char *base = support_create_and_chdir_toolong_temp_directory (BASENAME);
- char buf[PATH_MAX + 1];
- const char *res = realpath (".", buf);
+ char buf;
+ const char *res = realpath (".", &buf);
/* canonicalize.c states that if the real path is >= PATH_MAX, then
realpath returns NULL and sets ENAMETOOLONG. */
--
2.34.1
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH] tst-realpath-toolong: Fix hurd build
2022-01-22 14:45 ` [PATCH] tst-realpath-toolong: Fix hurd build Siddhesh Poyarekar
@ 2022-01-23 0:36 ` Samuel Thibault
2022-01-23 15:19 ` Siddhesh Poyarekar
0 siblings, 1 reply; 36+ messages in thread
From: Samuel Thibault @ 2022-01-23 0:36 UTC (permalink / raw)
To: Siddhesh Poyarekar; +Cc: libc-alpha, joseph
Siddhesh Poyarekar via Libc-alpha, le sam. 22 janv. 2022 20:15:23 +0530, a ecrit:
> We don't really need a bigger buffer for realpath since it should fail
> and return NULL. In the bug too, the buffer itself is not accessed; it
> is in fact left untouched. Drop the PATH_MAX use and pass a single char
> address.
? realpath assumes that the passed buffer is PATH_MAX-long. When
PATH_MAX is not defined, calling it with a buffer is essentially
undefined. Better just pass NULL.
> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
> ---
> stdlib/tst-realpath-toolong.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/stdlib/tst-realpath-toolong.c b/stdlib/tst-realpath-toolong.c
> index 8bed772460..ed84787a32 100644
> --- a/stdlib/tst-realpath-toolong.c
> +++ b/stdlib/tst-realpath-toolong.c
> @@ -34,8 +34,8 @@ do_test (void)
> {
> char *base = support_create_and_chdir_toolong_temp_directory (BASENAME);
>
> - char buf[PATH_MAX + 1];
> - const char *res = realpath (".", buf);
> + char buf;
> + const char *res = realpath (".", &buf);
>
> /* canonicalize.c states that if the real path is >= PATH_MAX, then
> realpath returns NULL and sets ENAMETOOLONG. */
> --
> 2.34.1
>
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH] tst-realpath-toolong: Fix hurd build
2022-01-23 0:36 ` Samuel Thibault
@ 2022-01-23 15:19 ` Siddhesh Poyarekar
2022-01-23 15:33 ` Samuel Thibault
0 siblings, 1 reply; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-23 15:19 UTC (permalink / raw)
To: Samuel Thibault; +Cc: libc-alpha, joseph
On 23/01/2022 06:06, Samuel Thibault wrote:
> Siddhesh Poyarekar via Libc-alpha, le sam. 22 janv. 2022 20:15:23 +0530, a ecrit:
>> We don't really need a bigger buffer for realpath since it should fail
>> and return NULL. In the bug too, the buffer itself is not accessed; it
>> is in fact left untouched. Drop the PATH_MAX use and pass a single char
>> address.
>
> ? realpath assumes that the passed buffer is PATH_MAX-long. When
> PATH_MAX is not defined, calling it with a buffer is essentially
> undefined. Better just pass NULL.
Passing NULL doesn't reproduce the problem because realpath just
allocates enough to accommodate the return, even when it exceeds
PATH_MAX. It only applies when a non-NULL buffer is supplied.
Would you prefer it if I defined PATH_MAX on hurd then, something like:
#ifndef PATH_MAX
# define PATH_MAX 1024
#endif
or do you prefer a more accurate path_max value using pathconf()?
The former will be a simpler fix, the latter will be best served by a
get_path_max support function, which will be more elaborate but
accurate. I'm happy to do either.
Thanks,
Siddhesh
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH] tst-realpath-toolong: Fix hurd build
2022-01-23 15:19 ` Siddhesh Poyarekar
@ 2022-01-23 15:33 ` Samuel Thibault
2022-01-24 6:00 ` [committed v2] " Siddhesh Poyarekar
0 siblings, 1 reply; 36+ messages in thread
From: Samuel Thibault @ 2022-01-23 15:33 UTC (permalink / raw)
To: Siddhesh Poyarekar; +Cc: libc-alpha, joseph
Siddhesh Poyarekar, le dim. 23 janv. 2022 20:49:48 +0530, a ecrit:
> On 23/01/2022 06:06, Samuel Thibault wrote:
> > Siddhesh Poyarekar via Libc-alpha, le sam. 22 janv. 2022 20:15:23 +0530, a ecrit:
> > > We don't really need a bigger buffer for realpath since it should fail
> > > and return NULL. In the bug too, the buffer itself is not accessed; it
> > > is in fact left untouched. Drop the PATH_MAX use and pass a single char
> > > address.
> >
> > ? realpath assumes that the passed buffer is PATH_MAX-long. When
> > PATH_MAX is not defined, calling it with a buffer is essentially
> > undefined. Better just pass NULL.
>
> Passing NULL doesn't reproduce the problem because realpath just allocates
> enough to accommodate the return, even when it exceeds PATH_MAX.
Ah, ok, sorry I didn't check the whole story.
> Would you prefer it if I defined PATH_MAX on hurd then, something like:
>
> #ifndef PATH_MAX
> # define PATH_MAX 1024
> #endif
>
> or do you prefer a more accurate path_max value using pathconf()?
Better use the accurate from pathconf() ; that being said it will return
-1 on the ext2fs filesystem, so we'll have to resort to a hardcoded
limit in that case anyway. I'm fine with just setting PATH_MAX by hand
here.
Samuel
^ permalink raw reply [flat|nested] 36+ messages in thread
* [committed v2] tst-realpath-toolong: Fix hurd build
2022-01-23 15:33 ` Samuel Thibault
@ 2022-01-24 6:00 ` Siddhesh Poyarekar
0 siblings, 0 replies; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-24 6:00 UTC (permalink / raw)
To: libc-alpha; +Cc: Samuel Thibault
Thanks, I've committed this after confirming that build-many-glibcs
works for i686-gnu.
-->8--
Define PATH_MAX to a constant if it isn't already defined, like in hurd.
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
stdlib/tst-realpath-toolong.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/stdlib/tst-realpath-toolong.c b/stdlib/tst-realpath-toolong.c
index 8bed772460..4388890294 100644
--- a/stdlib/tst-realpath-toolong.c
+++ b/stdlib/tst-realpath-toolong.c
@@ -29,6 +29,10 @@
#define BASENAME "tst-realpath-toolong."
+#ifndef PATH_MAX
+# define PATH_MAX 1024
+#endif
+
int
do_test (void)
{
--
2.34.1
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v5] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999)
2022-01-21 18:04 ` [PATCH v5] " Siddhesh Poyarekar
@ 2022-01-24 6:03 ` Siddhesh Poyarekar
0 siblings, 0 replies; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-24 6:03 UTC (permalink / raw)
To: libc-alpha; +Cc: Qualys Security Advisory, Andreas Schwab
On 21/01/2022 23:34, Siddhesh Poyarekar via Libc-alpha wrote:
> No valid path returned by getcwd would fit into 1 byte, so reject the
> size early and return NULL with errno set to ERANGE. This change is
> prompted by CVE-2021-3999, which describes a single byte buffer
> underflow and overflow when all of the following conditions are met:
>
> - The buffer size (i.e. the second argument of getcwd) is 1 byte
> - The current working directory is too long
> - '/' is also mounted on the current working directory
>
> Sequence of events:
>
> - In sysdeps/unix/sysv/linux/getcwd.c, the syscall returns ENAMETOOLONG
> because the linux kernel checks for name length before it checks
> buffer size
>
> - The code falls back to the generic getcwd in sysdeps/posix
>
> - In the generic func, the buf[0] is set to '\0' on line 250
>
> - this while loop on line 262 is bypassed:
>
> while (!(thisdev == rootdev && thisino == rootino))
>
> since the rootfs (/) is bind mounted onto the directory and the flow
> goes on to line 449, where it puts a '/' in the byte before the
> buffer.
>
> - Finally on line 458, it moves 2 bytes (the underflowed byte and the
> '\0') to the buf[0] and buf[1], resulting in a 1 byte buffer overflow.
>
> - buf is returned on line 469 and errno is not set.
>
> This resolves BZ #28769.
>
> Reviewed-by: Andreas Schwab <schwab@linux-m68k.org>
> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> Signed-off-by: Qualys Security Advisory <qsa@qualys.com>
> Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Pushed now since updates were trivial and Adhemerval and Andreas had
already acked the rest.
Thanks,
Siddhesh
> ---
> NEWS | 6 +
> sysdeps/posix/getcwd.c | 7 +
> sysdeps/unix/sysv/linux/Makefile | 7 +-
> .../unix/sysv/linux/tst-getcwd-smallbuff.c | 241 ++++++++++++++++++
> 4 files changed, 260 insertions(+), 1 deletion(-)
> create mode 100644 sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
>
> diff --git a/NEWS b/NEWS
> index 4c392a445e..07e9eac52d 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -170,6 +170,12 @@ Security related changes:
> function could result in a memory leak and potential access of
> uninitialized memory. Reported by Qualys.
>
> + CVE-2021-3999: Passing a buffer of size exactly 1 byte to the getcwd
> + function may result in an off-by-one buffer underflow and overflow
> + when the current working directory is longer than PATH_MAX and also
> + corresponds to the / directory through an unprivileged mount
> + namespace. Reported by Qualys.
> +
> The following bugs are resolved with this release:
>
> [The release manager will add the list generated by
> diff --git a/sysdeps/posix/getcwd.c b/sysdeps/posix/getcwd.c
> index e147a31a81..9d5787b6f4 100644
> --- a/sysdeps/posix/getcwd.c
> +++ b/sysdeps/posix/getcwd.c
> @@ -187,6 +187,13 @@ __getcwd_generic (char *buf, size_t size)
> size_t allocated = size;
> size_t used;
>
> + /* A size of 1 byte is never useful. */
> + if (allocated == 1)
> + {
> + __set_errno (ERANGE);
> + return NULL;
> + }
> +
> #if HAVE_MINIMALLY_WORKING_GETCWD
> /* If AT_FDCWD is not defined, the algorithm below is O(N**2) and
> this is much slower than the system getcwd (at least on
> diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
> index 85fc8cbf75..7ca9350c99 100644
> --- a/sysdeps/unix/sysv/linux/Makefile
> +++ b/sysdeps/unix/sysv/linux/Makefile
> @@ -346,7 +346,12 @@ sysdep_routines += xstatconv internal_statvfs \
>
> sysdep_headers += bits/fcntl-linux.h
>
> -tests += tst-fallocate tst-fallocate64 tst-o_path-locks
> +tests += \
> + tst-fallocate \
> + tst-fallocate64 \
> + tst-getcwd-smallbuff \
> + tst-o_path-locks \
> +# tests
> endif
>
> ifeq ($(subdir),elf)
> diff --git a/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
> new file mode 100644
> index 0000000000..d460d6e766
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/tst-getcwd-smallbuff.c
> @@ -0,0 +1,241 @@
> +/* Verify that getcwd returns ERANGE for size 1 byte and does not underflow
> + buffer when the CWD is too long and is also a mount target of /. See bug
> + #28769 or CVE-2021-3999 for more context.
> + Copyright The GNU Toolchain Authors.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <https://www.gnu.org/licenses/>. */
> +
> +#include <errno.h>
> +#include <fcntl.h>
> +#include <intprops.h>
> +#include <limits.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/mount.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +#include <sys/wait.h>
> +
> +#include <sys/socket.h>
> +#include <sys/un.h>
> +#include <support/check.h>
> +#include <support/temp_file.h>
> +#include <support/xsched.h>
> +#include <support/xunistd.h>
> +
> +static char *base;
> +#define BASENAME "tst-getcwd-smallbuff"
> +#define MOUNT_NAME "mpoint"
> +static int sockfd[2];
> +
> +static void
> +do_cleanup (void)
> +{
> + support_chdir_toolong_temp_directory (base);
> + TEST_VERIFY_EXIT (rmdir (MOUNT_NAME) == 0);
> + free (base);
> +}
> +
> +static void
> +send_fd (const int sock, const int fd)
> +{
> + struct msghdr msg = {0};
> + union
> + {
> + struct cmsghdr hdr;
> + char buf[CMSG_SPACE (sizeof (int))];
> + } cmsgbuf = {0};
> + struct cmsghdr *cmsg;
> + struct iovec vec;
> + char ch = 'A';
> + ssize_t n;
> +
> + msg.msg_control = &cmsgbuf.buf;
> + msg.msg_controllen = sizeof (cmsgbuf.buf);
> +
> + cmsg = CMSG_FIRSTHDR (&msg);
> + cmsg->cmsg_len = CMSG_LEN (sizeof (int));
> + cmsg->cmsg_level = SOL_SOCKET;
> + cmsg->cmsg_type = SCM_RIGHTS;
> + memcpy (CMSG_DATA (cmsg), &fd, sizeof (fd));
> +
> + vec.iov_base = &ch;
> + vec.iov_len = 1;
> + msg.msg_iov = &vec;
> + msg.msg_iovlen = 1;
> +
> + while ((n = sendmsg (sock, &msg, 0)) == -1 && errno == EINTR);
> +
> + TEST_VERIFY_EXIT (n == 1);
> +}
> +
> +static int
> +recv_fd (const int sock)
> +{
> + struct msghdr msg = {0};
> + union
> + {
> + struct cmsghdr hdr;
> + char buf[CMSG_SPACE(sizeof(int))];
> + } cmsgbuf = {0};
> + struct cmsghdr *cmsg;
> + struct iovec vec;
> + ssize_t n;
> + char ch = '\0';
> + int fd = -1;
> +
> + vec.iov_base = &ch;
> + vec.iov_len = 1;
> + msg.msg_iov = &vec;
> + msg.msg_iovlen = 1;
> +
> + msg.msg_control = &cmsgbuf.buf;
> + msg.msg_controllen = sizeof (cmsgbuf.buf);
> +
> + while ((n = recvmsg (sock, &msg, 0)) == -1 && errno == EINTR);
> + if (n != 1 || ch != 'A')
> + return -1;
> +
> + cmsg = CMSG_FIRSTHDR (&msg);
> + if (cmsg == NULL)
> + return -1;
> + if (cmsg->cmsg_type != SCM_RIGHTS)
> + return -1;
> + memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
> + if (fd < 0)
> + return -1;
> + return fd;
> +}
> +
> +static int
> +child_func (void * const arg)
> +{
> + xclose (sockfd[0]);
> + const int sock = sockfd[1];
> + char ch;
> +
> + TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
> + TEST_VERIFY_EXIT (ch == '1');
> +
> + if (mount ("/", MOUNT_NAME, NULL, MS_BIND | MS_REC, NULL))
> + FAIL_EXIT1 ("mount failed: %m\n");
> + const int fd = xopen ("mpoint",
> + O_RDONLY | O_PATH | O_DIRECTORY | O_NOFOLLOW, 0);
> +
> + send_fd (sock, fd);
> + xclose (fd);
> +
> + TEST_VERIFY_EXIT (read (sock, &ch, 1) == 1);
> + TEST_VERIFY_EXIT (ch == 'a');
> +
> + xclose (sock);
> + return 0;
> +}
> +
> +static void
> +update_map (char * const mapping, const char * const map_file)
> +{
> + const size_t map_len = strlen (mapping);
> +
> + const int fd = xopen (map_file, O_WRONLY, 0);
> + xwrite (fd, mapping, map_len);
> + xclose (fd);
> +}
> +
> +static void
> +proc_setgroups_write (const long child_pid, const char * const str)
> +{
> + const size_t str_len = strlen(str);
> +
> + char setgroups_path[sizeof ("/proc//setgroups") + INT_STRLEN_BOUND (long)];
> +
> + snprintf (setgroups_path, sizeof (setgroups_path),
> + "/proc/%ld/setgroups", child_pid);
> +
> + const int fd = open (setgroups_path, O_WRONLY);
> +
> + if (fd < 0)
> + {
> + TEST_VERIFY_EXIT (errno == ENOENT);
> + FAIL_UNSUPPORTED ("/proc/%ld/setgroups not found\n", child_pid);
> + }
> +
> + xwrite (fd, str, str_len);
> + xclose(fd);
> +}
> +
> +static char child_stack[1024 * 1024];
> +
> +int
> +do_test (void)
> +{
> + base = support_create_and_chdir_toolong_temp_directory (BASENAME);
> +
> + xmkdir (MOUNT_NAME, S_IRWXU);
> + atexit (do_cleanup);
> +
> + TEST_VERIFY_EXIT (socketpair (AF_UNIX, SOCK_STREAM, 0, sockfd) == 0);
> + pid_t child_pid = xclone (child_func, NULL, child_stack,
> + sizeof (child_stack),
> + CLONE_NEWUSER | CLONE_NEWNS | SIGCHLD);
> +
> + xclose (sockfd[1]);
> + const int sock = sockfd[0];
> +
> + char map_path[sizeof ("/proc//uid_map") + INT_STRLEN_BOUND (long)];
> + char map_buf[sizeof ("0 1") + INT_STRLEN_BOUND (long)];
> +
> + snprintf (map_path, sizeof (map_path), "/proc/%ld/uid_map",
> + (long) child_pid);
> + snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getuid());
> + update_map (map_buf, map_path);
> +
> + proc_setgroups_write ((long) child_pid, "deny");
> + snprintf (map_path, sizeof (map_path), "/proc/%ld/gid_map",
> + (long) child_pid);
> + snprintf (map_buf, sizeof (map_buf), "0 %ld 1", (long) getgid());
> + update_map (map_buf, map_path);
> +
> + TEST_VERIFY_EXIT (send (sock, "1", 1, MSG_NOSIGNAL) == 1);
> + const int fd = recv_fd (sock);
> + TEST_VERIFY_EXIT (fd >= 0);
> + TEST_VERIFY_EXIT (fchdir (fd) == 0);
> +
> + static char buf[2 * 10 + 1];
> + memset (buf, 'A', sizeof (buf));
> +
> + /* Finally, call getcwd and check if it resulted in a buffer underflow. */
> + char * cwd = getcwd (buf + sizeof (buf) / 2, 1);
> + TEST_VERIFY (cwd == NULL);
> + TEST_VERIFY (errno == ERANGE);
> +
> + for (int i = 0; i < sizeof (buf); i++)
> + if (buf[i] != 'A')
> + {
> + printf ("buf[%d] = %02x\n", i, (unsigned int) buf[i]);
> + support_record_failure ();
> + }
> +
> + TEST_VERIFY_EXIT (send (sock, "a", 1, MSG_NOSIGNAL) == 1);
> + xclose (sock);
> + TEST_VERIFY_EXIT (xwaitpid (child_pid, NULL, 0) == child_pid);
> +
> + return 0;
> +}
> +
> +#define CLEANUP_HANDLER do_cleanup
> +#include <support/test-driver.c>
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770]
2022-01-20 9:32 ` [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770] Siddhesh Poyarekar
2022-01-21 23:22 ` Joseph Myers
@ 2022-01-24 13:45 ` Andreas Schwab
2022-01-24 14:25 ` Siddhesh Poyarekar
1 sibling, 1 reply; 36+ messages in thread
From: Andreas Schwab @ 2022-01-24 13:45 UTC (permalink / raw)
To: Siddhesh Poyarekar via Libc-alpha; +Cc: Siddhesh Poyarekar, fweimer
On Jan 20 2022, Siddhesh Poyarekar via Libc-alpha wrote:
> diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
> index f36bdf4c76..732dc7ea46 100644
> --- a/stdlib/canonicalize.c
> +++ b/stdlib/canonicalize.c
> @@ -400,8 +400,16 @@ realpath_stk (const char *name, char *resolved,
>
> error:
> *dest++ = '\0';
> - if (resolved != NULL && dest - rname <= get_path_max ())
> - rname = strcpy (resolved, rname);
> + if (resolved != NULL)
> + {
> + if (dest - rname <= get_path_max ())
> + rname = strcpy (resolved, rname);
> + else
> + {
> + failed = true;
> + __set_errno (ENAMETOOLONG);
> + }
> + }
Shouldn't that preserve any preexisting error? I think the result
should only be copied if !failed.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770]
2022-01-24 13:45 ` [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770] Andreas Schwab
@ 2022-01-24 14:25 ` Siddhesh Poyarekar
2022-01-24 14:48 ` Andreas Schwab
0 siblings, 1 reply; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-24 14:25 UTC (permalink / raw)
To: Andreas Schwab, Siddhesh Poyarekar via Libc-alpha; +Cc: fweimer
On 24/01/2022 19:15, Andreas Schwab wrote:
> On Jan 20 2022, Siddhesh Poyarekar via Libc-alpha wrote:
>
>> diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
>> index f36bdf4c76..732dc7ea46 100644
>> --- a/stdlib/canonicalize.c
>> +++ b/stdlib/canonicalize.c
>> @@ -400,8 +400,16 @@ realpath_stk (const char *name, char *resolved,
>>
>> error:
>> *dest++ = '\0';
>> - if (resolved != NULL && dest - rname <= get_path_max ())
>> - rname = strcpy (resolved, rname);
>> + if (resolved != NULL)
>> + {
>> + if (dest - rname <= get_path_max ())
>> + rname = strcpy (resolved, rname);
>> + else
>> + {
>> + failed = true;
>> + __set_errno (ENAMETOOLONG);
>> + }
>> + }
>
> Shouldn't that preserve any preexisting error?
like this?
diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
index 732dc7ea46..6caed9e70e 100644
--- a/stdlib/canonicalize.c
+++ b/stdlib/canonicalize.c
@@ -404,7 +404,7 @@ error:
{
if (dest - rname <= get_path_max ())
rname = strcpy (resolved, rname);
- else
+ else if (!failed)
{
failed = true;
__set_errno (ENAMETOOLONG);
> I think the result
> should only be copied if !failed.
>
Looks like tests in test-canon.c depend on buf contents having being
copied in despite failure.
Siddhesh
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770]
2022-01-24 14:25 ` Siddhesh Poyarekar
@ 2022-01-24 14:48 ` Andreas Schwab
2022-01-24 14:59 ` Siddhesh Poyarekar
0 siblings, 1 reply; 36+ messages in thread
From: Andreas Schwab @ 2022-01-24 14:48 UTC (permalink / raw)
To: Siddhesh Poyarekar; +Cc: Siddhesh Poyarekar via Libc-alpha, fweimer
On Jan 24 2022, Siddhesh Poyarekar wrote:
> Looks like tests in test-canon.c depend on buf contents having being
> copied in despite failure.
That is not supported by POSIX.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770]
2022-01-24 14:48 ` Andreas Schwab
@ 2022-01-24 14:59 ` Siddhesh Poyarekar
2022-01-24 15:28 ` Andreas Schwab
0 siblings, 1 reply; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-24 14:59 UTC (permalink / raw)
To: Andreas Schwab; +Cc: fweimer, Siddhesh Poyarekar via Libc-alpha
On 24/01/2022 20:18, Andreas Schwab wrote:
> On Jan 24 2022, Siddhesh Poyarekar wrote:
>
>> Looks like tests in test-canon.c depend on buf contents having being
>> copied in despite failure.
>
> That is not supported by POSIX.
>
OK, I'll file a separate bug and fix for it then. Is the fix I posted
sufficient for your other concern, i.e. not overriding preexisting error?
Thanks,
Siddhesh
^ permalink raw reply [flat|nested] 36+ messages in thread
* Re: [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770]
2022-01-24 14:59 ` Siddhesh Poyarekar
@ 2022-01-24 15:28 ` Andreas Schwab
2022-01-24 16:08 ` [committed] realpath: Avoid overwriting preexisting error (CVE-2021-3998) Siddhesh Poyarekar
0 siblings, 1 reply; 36+ messages in thread
From: Andreas Schwab @ 2022-01-24 15:28 UTC (permalink / raw)
To: Siddhesh Poyarekar; +Cc: fweimer, Siddhesh Poyarekar via Libc-alpha
On Jan 24 2022, Siddhesh Poyarekar wrote:
> Is the fix I posted sufficient for your other concern, i.e. not
> overriding preexisting error?
Yes.
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
^ permalink raw reply [flat|nested] 36+ messages in thread
* [committed] realpath: Avoid overwriting preexisting error (CVE-2021-3998)
2022-01-24 15:28 ` Andreas Schwab
@ 2022-01-24 16:08 ` Siddhesh Poyarekar
0 siblings, 0 replies; 36+ messages in thread
From: Siddhesh Poyarekar @ 2022-01-24 16:08 UTC (permalink / raw)
To: libc-alpha; +Cc: Andreas Schwab
Set errno and failure for paths that are too long only if no other error
occurred earlier.
Related: BZ #28770
Reviewed-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
---
stdlib/canonicalize.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
index 732dc7ea46..6caed9e70e 100644
--- a/stdlib/canonicalize.c
+++ b/stdlib/canonicalize.c
@@ -404,7 +404,7 @@ error:
{
if (dest - rname <= get_path_max ())
rname = strcpy (resolved, rname);
- else
+ else if (!failed)
{
failed = true;
__set_errno (ENAMETOOLONG);
--
2.34.1
^ permalink raw reply [flat|nested] 36+ messages in thread
end of thread, other threads:[~2022-01-24 16:18 UTC | newest]
Thread overview: 36+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-01-19 8:21 [PATCH v2 0/3] Fixes for CVE-2021-3998 and CVE-2021-3999 Siddhesh Poyarekar
2022-01-19 8:21 ` [PATCH v2 1/3] support: Add helpers to create paths longer than PATH_MAX Siddhesh Poyarekar
2022-01-19 10:13 ` Siddhesh Poyarekar
2022-01-20 14:47 ` Cristian Rodríguez
2022-01-20 14:56 ` Florian Weimer
2022-01-20 15:17 ` Cristian Rodríguez
2022-01-20 14:57 ` Siddhesh Poyarekar
2022-01-19 8:21 ` [PATCH v2 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX (CVE-2021-3998) Siddhesh Poyarekar
2022-01-19 8:21 ` [PATCH v2 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999) Siddhesh Poyarekar
2022-01-20 9:32 ` [PATCH v3 0/3] Fixes for CVE-2021-3998 and CVE-2021-3999 Siddhesh Poyarekar
2022-01-20 9:32 ` [PATCH v3 1/3] support: Add helpers to create paths longer than PATH_MAX Siddhesh Poyarekar
2022-01-21 16:27 ` Adhemerval Zanella
2022-01-20 9:32 ` [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770] Siddhesh Poyarekar
2022-01-21 23:22 ` Joseph Myers
2022-01-22 3:47 ` Siddhesh Poyarekar
2022-01-22 14:45 ` [PATCH] tst-realpath-toolong: Fix hurd build Siddhesh Poyarekar
2022-01-23 0:36 ` Samuel Thibault
2022-01-23 15:19 ` Siddhesh Poyarekar
2022-01-23 15:33 ` Samuel Thibault
2022-01-24 6:00 ` [committed v2] " Siddhesh Poyarekar
2022-01-24 13:45 ` [PATCH v3 2/3] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770] Andreas Schwab
2022-01-24 14:25 ` Siddhesh Poyarekar
2022-01-24 14:48 ` Andreas Schwab
2022-01-24 14:59 ` Siddhesh Poyarekar
2022-01-24 15:28 ` Andreas Schwab
2022-01-24 16:08 ` [committed] realpath: Avoid overwriting preexisting error (CVE-2021-3998) Siddhesh Poyarekar
2022-01-20 9:32 ` [PATCH v3 3/3] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999) Siddhesh Poyarekar
2022-01-20 13:32 ` Andreas Schwab
2022-01-21 16:41 ` Adhemerval Zanella
2022-01-21 17:26 ` Siddhesh Poyarekar
2022-01-21 17:31 ` Adhemerval Zanella
2022-01-21 17:38 ` [PATCH v4] " Siddhesh Poyarekar
2022-01-21 17:59 ` Andreas Schwab
2022-01-21 18:02 ` Siddhesh Poyarekar
2022-01-21 18:04 ` [PATCH v5] " Siddhesh Poyarekar
2022-01-24 6:03 ` Siddhesh Poyarekar
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