This is a note to let you know that I've just added the patch titled
gen_init_cpio: avoid stack overflow when expanding
to the 3.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
gen_init_cpio-avoid-stack-overflow-when-expanding.patch
and it can be found in the queue-3.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 20f1de659b77364d55d4e7fad2ef657e7730323f Mon Sep 17 00:00:00 2001
From: Kees Cook <[email protected]>
Date: Thu, 25 Oct 2012 13:38:14 -0700
Subject: gen_init_cpio: avoid stack overflow when expanding
From: Kees Cook <[email protected]>
commit 20f1de659b77364d55d4e7fad2ef657e7730323f upstream.
Fix possible overflow of the buffer used for expanding environment
variables when building file list.
In the extremely unlikely case of an attacker having control over the
environment variables visible to gen_init_cpio, control over the
contents of the file gen_init_cpio parses, and gen_init_cpio was built
without compiler hardening, the attacker can gain arbitrary execution
control via a stack buffer overflow.
$ cat usr/crash.list
file foo ${BIG}${BIG}${BIG}${BIG}${BIG}${BIG} 0755 0 0
$ BIG=$(perl -e 'print "A" x 4096;') ./usr/gen_init_cpio usr/crash.list
*** buffer overflow detected ***: ./usr/gen_init_cpio terminated
This also replaces the space-indenting with tabs.
Patch based on existing fix extracted from grsecurity.
Signed-off-by: Kees Cook <[email protected]>
Cc: Michal Marek <[email protected]>
Cc: Brad Spengler <[email protected]>
Cc: PaX Team <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
usr/gen_init_cpio.c | 41 ++++++++++++++++++++++-------------------
1 file changed, 22 insertions(+), 19 deletions(-)
--- a/usr/gen_init_cpio.c
+++ b/usr/gen_init_cpio.c
@@ -303,7 +303,7 @@ static int cpio_mkfile(const char *name,
int retval;
int rc = -1;
int namesize;
- int i;
+ unsigned int i;
mode |= S_IFREG;
@@ -381,25 +381,28 @@ error:
static char *cpio_replace_env(char *new_location)
{
- char expanded[PATH_MAX + 1];
- char env_var[PATH_MAX + 1];
- char *start;
- char *end;
-
- for (start = NULL; (start = strstr(new_location, "${")); ) {
- end = strchr(start, '}');
- if (start < end) {
- *env_var = *expanded = '\0';
- strncat(env_var, start + 2, end - start - 2);
- strncat(expanded, new_location, start - new_location);
- strncat(expanded, getenv(env_var), PATH_MAX);
- strncat(expanded, end + 1, PATH_MAX);
- strncpy(new_location, expanded, PATH_MAX);
- } else
- break;
- }
+ char expanded[PATH_MAX + 1];
+ char env_var[PATH_MAX + 1];
+ char *start;
+ char *end;
+
+ for (start = NULL; (start = strstr(new_location, "${")); ) {
+ end = strchr(start, '}');
+ if (start < end) {
+ *env_var = *expanded = '\0';
+ strncat(env_var, start + 2, end - start - 2);
+ strncat(expanded, new_location, start - new_location);
+ strncat(expanded, getenv(env_var),
+ PATH_MAX - strlen(expanded));
+ strncat(expanded, end + 1,
+ PATH_MAX - strlen(expanded));
+ strncpy(new_location, expanded, PATH_MAX);
+ new_location[PATH_MAX] = 0;
+ } else
+ break;
+ }
- return new_location;
+ return new_location;
}
Patches currently in stable-queue which might be from [email protected] are
queue-3.6/gen_init_cpio-avoid-stack-overflow-when-expanding.patch
queue-3.6/vfs-don-t-do-protected-sym-hard-links-by-default.patch
queue-3.6/fs-compat_ioctl.c-video_set_spu_palette-missing-error-check.patch
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