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authorKees Cook <keescook@chromium.org>2012-10-25 13:38:14 -0700
committerBen Hutchings <ben@decadent.org.uk>2012-10-30 23:27:07 +0000
commit4253a4a1c331f534be64365524e88f317c7f0824 (patch)
treec317fed7005a22a7194f7f2c8780a0066878623f
parent4b77f431a837ebaf54757083425a9ce38dab5488 (diff)
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=$(perl -e 'print "A" x 4096;') ./usr/gen_init_cpio usr/crash.list *** buffer overflow detected ***: ./usr/gen_init_cpio terminated This also replaces the space-indenting with tabs. Patch based on existing fix extracted from grsecurity. Signed-off-by: Kees Cook <keescook@chromium.org> Cc: Michal Marek <mmarek@suse.cz> Cc: Brad Spengler <spender@grsecurity.net> Cc: PaX Team <pageexec@freemail.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
-rw-r--r--usr/gen_init_cpio.c43
1 files changed, 23 insertions, 20 deletions
diff --git a/usr/gen_init_cpio.c b/usr/gen_init_cpio.c
index af0f22fb1ef7..aca6edcbbc6f 100644
--- a/usr/gen_init_cpio.c
+++ b/usr/gen_init_cpio.c
@@ -303,7 +303,7 @@ static int cpio_mkfile(const char *name, const char *location,
int retval;
int rc = -1;
int namesize;
- int i;
+ unsigned int i;
mode |= S_IFREG;
@@ -381,25 +381,28 @@ error:
static char *cpio_replace_env(char *new_location)
{
- char expanded[PATH_MAX + 1];
- char env_var[PATH_MAX + 1];
- char *start;
- char *end;
-
- for (start = NULL; (start = strstr(new_location, "${")); ) {
- 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;
}