| title: | PATCH exec argument expansion can inappropr |
|
Brad Spengler published a local memory-allocation DoS that
evades the OOM-killer (though not the virtual memory RLIMIT):
rel="nofollow" www.grsecurity.net/~spender/64bit_dos.c www.grsecurity.net/~spender/64bit_dos.c
The recent changes to create a stack guard page helps slightly to
discourage this attack, but it is not sufficient. Compiling it statically
moves the libraries out of the way, allowing the stack VMA to fill the
entire TASK_SIZE.
There are two issues:
1) the OOM killer doesnt notice this argv memory explosion
2) the argv expansion does not check if rlim[RLIMIT_STACK].rlim_cur is -1.
I figure a quick solution for #2 would be the following patch. However,
running multiple copies of this program could result in similar OOM
behavior, so issue #1 still needs a solution.
Reported-by: Brad Spengler <spender@xxxxxxxxxxxxxx
Signed-off-by: Kees Cook <kees.cook@xxxxxxxxxxxxx
---
fs/exec.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/fs/exec.c b/fs/exec.c
index dab85ec..be40063 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -194,7 +194,8 @@ static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
* to work from.
*/
rlim = current- signal- rlim;
- if (size ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) {
+ if (size ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4 ||
+ size TASK_SIZE / 4) {
put_page(page);
return NULL;
}
--
1.7.1
--
Kees Cook
Ubuntu Security Team
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at rel="nofollow" vger.kernel.org/majordomo-info.html vger.kernel.org/majordomo-info.html
|
