I ran gcc's -fsanitize=address against coreutils, and two
sort tests failed due to buffer overruns. Both arose via
a bug in quotearg.c. Patch below. Two things remain to do:
1) find when the bug was introduced (before push)
2) address the module-factoring FIXME comment (after)
Not sure I'll do #1, but I will get to #2.
>From 5f14f49f770258fd81cea53602a94be0c0c4dffd Mon Sep 17 00:00:00 2001
From: Jim Meyering <meyer...@fb.com>
Date: Sat, 11 May 2013 18:43:50 -0700
Subject: [PATCH] quotearg: do not read beyond end of buffer
* lib/quotearg.c (quotearg_buffer_restyled): Do not read beyond the
end of an ARG for which no length was specified. With an N-byte
quote string, (e.g., N is 3 in the fr_FR.UTF-8 locale), this function
would read N-2 bytes beyond ARG's trailing NUL. This was triggered
via coreutils' misc/sort-debug-keys.sh test and detected by running
the test against a binary compiled with gcc-4.8.0's -fsanitize=address.
* tests/test-quotearg-simple.c (main): Add a test that triggers the bug.
* modules/quotearg-simple-tests (Files): Add tests/zerosize-ptr.h.
---
ChangeLog | 12 ++++++++++++
lib/quotearg.c | 7 ++++++-
modules/quotearg-simple-tests | 6 ++++++
tests/test-quotearg-simple.c | 35 +++++++++++++++++++++++++++++++++++
4 files changed, 59 insertions(+), 1 deletion(-)
diff --git a/ChangeLog b/ChangeLog
index 94cc0d8..2c65171 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2013-05-11 Jim Meyering <meyer...@fb.com>
+
+ quotearg: do not read beyond end of buffer
+ * lib/quotearg.c (quotearg_buffer_restyled): Do not read beyond the
+ end of an ARG for which no length was specified. With an N-byte
+ quote string, (e.g., N is 3 in the fr_FR.UTF-8 locale), this function
+ would read N-2 bytes beyond ARG's trailing NUL. This was triggered
+ via coreutils' misc/sort-debug-keys.sh test and detected by running
+ the test against a binary compiled with gcc-4.8.0's -fsanitize=address.
+ * tests/test-quotearg-simple.c (main): Add a test that triggers the bug.
+ * modules/quotearg-simple-tests (Files): Add tests/zerosize-ptr.h.
+
2013-05-11 Daiki Ueno <u...@gnu.org>
lock: work around pthread recursive mutexes bug in Mac OS X 10.6
diff --git a/lib/quotearg.c b/lib/quotearg.c
index 57a8382..40114d7 100644
--- a/lib/quotearg.c
+++ b/lib/quotearg.c
@@ -348,7 +348,12 @@ quotearg_buffer_restyled (char *buffer, size_t buffersize,
if (backslash_escapes
&& quote_string_len
- && i + quote_string_len <= argsize
+ && (i + quote_string_len
+ <= (argsize == SIZE_MAX && 1 < quote_string_len
+ /* Use strlen only if we must: when argsize is SIZE_MAX,
+ and when the quote string is more than 1 byte long.
+ If we do call strlen, save the result. */
+ ? (argsize = strlen (arg)) : argsize))
&& memcmp (arg + i, quote_string, quote_string_len) == 0)
{
if (elide_outer_quotes)
diff --git a/modules/quotearg-simple-tests b/modules/quotearg-simple-tests
index 0ef151d..e27bf24 100644
--- a/modules/quotearg-simple-tests
+++ b/modules/quotearg-simple-tests
@@ -2,12 +2,18 @@ Files:
tests/test-quotearg-simple.c
tests/test-quotearg.h
tests/macros.h
+tests/zerosize-ptr.h
Depends-on:
progname
stdint
configure.ac:
+dnl Check for prerequisites for memory fence checks.
+dnl FIXME: zerosize-ptr.h requires these: make a module for it
+gl_FUNC_MMAP_ANON
+AC_CHECK_HEADERS_ONCE([sys/mman.h])
+AC_CHECK_FUNCS_ONCE([mprotect])
Makefile.am:
TESTS += test-quotearg-simple
diff --git a/tests/test-quotearg-simple.c b/tests/test-quotearg-simple.c
index e7aa8fb..fe860ed 100644
--- a/tests/test-quotearg-simple.c
+++ b/tests/test-quotearg-simple.c
@@ -29,6 +29,7 @@
#include "localcharset.h"
#include "progname.h"
#include "macros.h"
+#include "zerosize-ptr.h"
#include "test-quotearg.h"
@@ -297,6 +298,40 @@ main (int argc _GL_UNUSED, char *argv[])
ascii_only);
}
+ {
+ /* Trigger the bug whereby quotearg_buffer would read beyond the NUL
+ that defines the end of the string being quoted. Use an input
+ string whose NUL is the last byte before an unreadable page. */
+ char *z = zerosize_ptr ();
+
+ if (z)
+ {
+ size_t q_len = 1024;
+ char *q = malloc (q_len + 1);
+ char buf[10];
+ memset (q, 'Q', q_len);
+ q[q_len] = 0;
+
+ /* Z points to the boundary between a readable/writable page
+ and one that is neither readable nor writable. Position
+ our string so its NUL is at the end of the writable one. */
+ char const *str = "____";
+ size_t s_len = strlen (str);
+ z -= s_len + 1;
+ memcpy (z, str, s_len + 1);
+
+ set_custom_quoting (NULL, q, q);
+ /* Whether this actually triggers a SEGV depends on the
+ implementation of memcmp: whether it compares only byte-at-
+ a-time, and from left to right (no SEGV) or some other way. */
+ size_t n = quotearg_buffer (buf, sizeof buf, z, SIZE_MAX, NULL);
+ ASSERT (n == s_len + 2 * q_len);
+ ASSERT (memcmp (buf, q, sizeof buf) == 0);
+ free (q);
+ }
+ }
+
quotearg_free ();
+
return 0;
}
--
1.8.3.rc1.44.gb387c77
