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authorKees Cook <keescook@chromium.org>2012-10-25 13:38:14 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-10-31 09:51:33 -0700
commited12438d94ded9c028570776898418adbb497f58 (patch)
treece92a47d837a94a5f72f172ed75443772385f103
parentd9ee258b13506301b6da6450cf7a1692826b471e (diff)
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gen_init_cpio: avoid stack overflow when expanding
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=$(perl -e 'print "A" x 4096;') ./usr/gen_init_cpio usr/crash.list *** buffer overflow detected ***: ./usr/gen_init_cpio terminated This also replaces the space-indenting with tabs. Patch based on existing fix extracted from grsecurity. Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Michal Marek <mmarek@suse.cz> Cc: Brad Spengler <spender@grsecurity.net> Cc: PaX Team <pageexec@freemail.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--usr/gen_init_cpio.c43
1 files changed, 23 insertions, 20 deletions
diff --git a/usr/gen_init_cpio.c b/usr/gen_init_cpio.c
index af0f22f..aca6edc 100644
--- a/usr/gen_init_cpio.c
+++ b/usr/gen_init_cpio.c
@@ -303,7 +303,7 @@ static int cpio_mkfile(const char *name, const char *location,
int retval;
int rc = -1;
int namesize;
- int i;
+ unsigned int i;
mode |= S_IFREG;
@@ -381,25 +381,28 @@ error:
static char *cpio_replace_env(char *new_location)
{
- char expanded[PATH_MAX + 1];
- char env_var[PATH_MAX + 1];
- char *start;
- char *end;
-
- for (start = NULL; (start = strstr(new_location, "${")); ) {
- 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;
- }
-
- return 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 - 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;
}