From: Aurelien Jarno <aurelien@aurel32.net>
To: libc-stable@sourceware.org
Cc: Paul Pluzhnikov <ppluzhnikov@google.com>
Subject: [2.24 COMMITTED 2/4] Fix BZ 22786: integer addition overflow may cause stack buffer overflow when realpath() input length is close to SSIZE_MAX.
Date: Mon, 01 Jan 2018 00:00:00 -0000 [thread overview]
Message-ID: <20181220233902.20796-2-aurelien@aurel32.net> (raw)
In-Reply-To: <20181220233902.20796-1-aurelien@aurel32.net>
From: Paul Pluzhnikov <ppluzhnikov@google.com>
2018-05-09 Paul Pluzhnikov <ppluzhnikov@google.com>
[BZ #22786]
* stdlib/canonicalize.c (__realpath): Fix overflow in path length
computation.
* stdlib/Makefile (test-bz22786): New test.
* stdlib/test-bz22786.c: New test.
(cherry picked from commit 5460617d1567657621107d895ee2dd83bc1f88f2)
---
ChangeLog | 8 ++++
NEWS | 2 +
stdlib/Makefile | 2 +-
stdlib/canonicalize.c | 2 +-
stdlib/test-bz22786.c | 90 +++++++++++++++++++++++++++++++++++++++++++
5 files changed, 102 insertions(+), 2 deletions(-)
create mode 100644 stdlib/test-bz22786.c
diff --git a/ChangeLog b/ChangeLog
index 63813de2d5..699e8e510e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2018-05-09 Paul Pluzhnikov <ppluzhnikov@google.com>
+
+ [BZ #22786]
+ * stdlib/canonicalize.c (__realpath): Fix overflow in path length
+ computation.
+ * stdlib/Makefile (test-bz22786): New test.
+ * stdlib/test-bz22786.c: New test.
+
2018-03-23 Andrew Senkevich <andrew.senkevich@intel.com>
Max Horn <max@quendi.de>
diff --git a/NEWS b/NEWS
index 77f7f1ad0e..0ff775e578 100644
--- a/NEWS
+++ b/NEWS
@@ -63,6 +63,8 @@ The following bugs are resolved with this release:
[22644] string: memmove-sse2-unaligned on 32bit x86 produces garbage when
crossing 2GB threshold (CVE-2017-18269)
[22715] x86-64: Properly align La_x86_64_retval to VEC_SIZE
+ [22786] libc: Stack buffer overflow in realpath() if input size is close
+ to SSIZE_MAX (CVE-2018-11236)
\f
Version 2.24
diff --git a/stdlib/Makefile b/stdlib/Makefile
index fc6f23dcaf..23f2d6e326 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -77,7 +77,7 @@ tests := tst-strtol tst-strtod testmb testrand testsort testdiv \
tst-tininess tst-strtod-underflow tst-tls-atexit \
tst-setcontext3 tst-tls-atexit-nodelete \
tst-strtol-locale tst-strtod-nan-locale tst-strfmon_l \
- tst-quick_exit tst-thread-quick_exit
+ tst-quick_exit tst-thread-quick_exit test-bz22786
tests-static := tst-secure-getenv
ifeq ($(have-cxx-thread_local),yes)
CFLAGS-tst-quick_exit.o = -std=c++11
diff --git a/stdlib/canonicalize.c b/stdlib/canonicalize.c
index 58bb8de949..59a7b942e0 100644
--- a/stdlib/canonicalize.c
+++ b/stdlib/canonicalize.c
@@ -181,7 +181,7 @@ __realpath (const char *name, char *resolved)
extra_buf = __alloca (path_max);
len = strlen (end);
- if ((long int) (n + len) >= path_max)
+ if (path_max - n <= len)
{
__set_errno (ENAMETOOLONG);
goto error;
diff --git a/stdlib/test-bz22786.c b/stdlib/test-bz22786.c
new file mode 100644
index 0000000000..e445034a8d
--- /dev/null
+++ b/stdlib/test-bz22786.c
@@ -0,0 +1,90 @@
+/* Bug 22786: test for buffer overflow in realpath.
+ Copyright (C) 2018 Free Software Foundation, Inc.
+ 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
+ <http://www.gnu.org/licenses/>. */
+
+/* This file must be run from within a directory called "stdlib". */
+
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <support/test-driver.h>
+#include <libc-internal.h>
+
+static int
+do_test (void)
+{
+ const char dir[] = "bz22786";
+ const char lnk[] = "bz22786/symlink";
+
+ rmdir (dir);
+ if (mkdir (dir, 0755) != 0 && errno != EEXIST)
+ {
+ printf ("mkdir %s: %m\n", dir);
+ return EXIT_FAILURE;
+ }
+ if (symlink (".", lnk) != 0 && errno != EEXIST)
+ {
+ printf ("symlink (%s, %s): %m\n", dir, lnk);
+ return EXIT_FAILURE;
+ }
+
+ const size_t path_len = (size_t) INT_MAX + 1;
+
+ DIAG_PUSH_NEEDS_COMMENT;
+#if __GNUC_PREREQ (7, 0)
+ /* GCC 7 warns about too-large allocations; here we need such
+ allocation to succeed for the test to work. */
+ DIAG_IGNORE_NEEDS_COMMENT (7, "-Walloc-size-larger-than=");
+#endif
+ char *path = malloc (path_len);
+ DIAG_POP_NEEDS_COMMENT;
+
+ if (path == NULL)
+ {
+ printf ("malloc (%zu): %m\n", path_len);
+ return EXIT_UNSUPPORTED;
+ }
+
+ /* Construct very long path = "bz22786/symlink/aaaa....." */
+ char *p = mempcpy (path, lnk, sizeof (lnk) - 1);
+ *(p++) = '/';
+ memset (p, 'a', path_len - (path - p) - 2);
+ p[path_len - (path - p) - 1] = '\0';
+
+ /* This call crashes before the fix for bz22786 on 32-bit platforms. */
+ p = realpath (path, NULL);
+
+ if (p != NULL || errno != ENAMETOOLONG)
+ {
+ printf ("realpath: %s (%m)", p);
+ return EXIT_FAILURE;
+ }
+
+ /* Cleanup. */
+ unlink (lnk);
+ rmdir (dir);
+
+ return 0;
+}
+
+#define TEST_FUNCTION do_test
+#include <support/test-driver.c>
--
2.19.2
next prev parent reply other threads:[~2018-12-20 23:39 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-01 0:00 [2.24 COMMITTED 1/4] Fix i386 memmove issue (bug 22644) Aurelien Jarno
2018-01-01 0:00 ` [2.24 COMMITTED 3/4] Don't write beyond destination in __mempcpy_avx512_no_vzeroupper (bug 23196) Aurelien Jarno
2018-01-01 0:00 ` Aurelien Jarno [this message]
2018-01-01 0:00 ` [2.24 COMMITTED 4/4] Add references to CVE-2017-18269, CVE-2018-11236, CVE-2018-11237 Aurelien Jarno
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181220233902.20796-2-aurelien@aurel32.net \
--to=aurelien@aurel32.net \
--cc=libc-stable@sourceware.org \
--cc=ppluzhnikov@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).