From: Aurelien Jarno <aurelien@aurel32.net>
To: libc-stable@sourceware.org
Cc: Siddhesh Poyarekar <siddhesh@sourceware.org>,
Adhemerval Zanella <adhemerval.zanella@linaro.org>
Subject: [COMMITTED 2.33 2/7] realpath: Set errno to ENAMETOOLONG for result larger than PATH_MAX [BZ #28770]
Date: Mon, 24 Jan 2022 23:48:52 +0100 [thread overview]
Message-ID: <20220124224857.3799610-2-aurelien@aurel32.net> (raw)
In-Reply-To: <20220124224857.3799610-1-aurelien@aurel32.net>
From: Siddhesh Poyarekar <siddhesh@sourceware.org>
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>
(cherry picked from commit ee8d5e33adb284601c00c94687bc907e10aec9bb)
---
NEWS | 5 ++++
stdlib/Makefile | 3 ++-
stdlib/canonicalize.c | 12 +++++++--
stdlib/tst-realpath-toolong.c | 49 +++++++++++++++++++++++++++++++++++
4 files changed, 66 insertions(+), 3 deletions(-)
create mode 100644 stdlib/tst-realpath-toolong.c
diff --git a/NEWS b/NEWS
index eba875d1f6..5352599d7f 100644
--- a/NEWS
+++ b/NEWS
@@ -26,6 +26,10 @@ 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:
[15271] dlfcn function failure after dlmopen terminates process
@@ -46,6 +50,7 @@ The following bugs are resolved with this release:
[28524] Conversion from ISO-2022-JP-3 with iconv may emit spurious NULs
[28532] powerpc64[le]: CFI for assembly templated syscalls is incorrect
[28768] CVE-2022-23218: Buffer overflow in sunrpc svcunix_create
+ [28770] CVE-2021-3998: Unexpected return value from realpath() for too long results
\f
Version 2.33
diff --git a/stdlib/Makefile b/stdlib/Makefile
index b3b30ab73e..b1eebd568f 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -86,7 +86,8 @@ tests := tst-strtol tst-strtod testmb testrand testsort testdiv \
tst-makecontext-align test-bz22786 tst-strtod-nan-sign \
tst-swapcontext1 tst-setcontext4 tst-setcontext5 \
tst-setcontext6 tst-setcontext7 tst-setcontext8 \
- tst-setcontext9 tst-bz20544 tst-canon-bz26341
+ tst-setcontext9 tst-bz20544 tst-canon-bz26341 \
+ tst-realpath-toolong
tests-internal := tst-strtod1i tst-strtod3 tst-strtod4 tst-strtod5i \
tst-tls-atexit tst-tls-atexit-nodelete
diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
index 698f9ede25..7a23a51b3a 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
next prev parent reply other threads:[~2022-01-24 22:49 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-24 22:48 [COMMITTED 2.33 1/7] support: Add helpers to create paths longer than PATH_MAX Aurelien Jarno
2022-01-24 22:48 ` Aurelien Jarno [this message]
2022-01-24 22:48 ` [COMMITTED 2.33 3/7] tst-realpath-toolong: Fix hurd build Aurelien Jarno
2022-01-24 22:48 ` [COMMITTED 2.33 4/7] support: Add xclone Aurelien Jarno
2022-01-24 22:48 ` [COMMITTED 2.33 5/7] getcwd: Set errno to ERANGE for size == 1 (CVE-2021-3999) Aurelien Jarno
2022-01-24 22:48 ` [COMMITTED 2.33 6/7] realpath: Avoid overwriting preexisting error (CVE-2021-3998) Aurelien Jarno
2022-01-24 22:48 ` [COMMITTED 2.33 7/7] Linux: Detect user namespace support in io/tst-getcwd-smallbuff Aurelien Jarno
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