* [Patch v2] mqueue: fix a use-after-free in sys_mq_notify()
@ 2017-07-09 20:19 Cong Wang
2017-07-09 21:37 ` Linus Torvalds
0 siblings, 1 reply; 2+ messages in thread
From: Cong Wang @ 2017-07-09 20:19 UTC (permalink / raw)
To: netdev
Cc: linux-kernel, geneblue.mail, Cong Wang, Andrew Morton,
Linus Torvalds, Manfred Spraul
The retry logic for netlink_attachskb() inside sys_mq_notify()
is nasty and vulnerable:
1) The sock refcnt is already released when retry is needed
2) The fd is controllable by user-space because we already
release the file refcnt
so we when retry but the fd has been just closed by user-space
during this small window, we end up calling netlink_detachskb()
on the error path which releases the sock again, later when
the user-space closes this socket a use-after-free could be
triggered.
Setting 'sock' to NULL here should be sufficient to fix it.
Reported-by: GeneBlue <geneblue.mail@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
---
ipc/mqueue.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index c9ff943..eb1391b 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -1270,8 +1270,10 @@ static int do_mq_notify(mqd_t mqdes, const struct sigevent *notification)
timeo = MAX_SCHEDULE_TIMEOUT;
ret = netlink_attachskb(sock, nc, &timeo, NULL);
- if (ret == 1)
+ if (ret == 1) {
+ sock = NULL;
goto retry;
+ }
if (ret) {
sock = NULL;
nc = NULL;
--
2.5.5
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [Patch v2] mqueue: fix a use-after-free in sys_mq_notify()
2017-07-09 20:19 [Patch v2] mqueue: fix a use-after-free in sys_mq_notify() Cong Wang
@ 2017-07-09 21:37 ` Linus Torvalds
0 siblings, 0 replies; 2+ messages in thread
From: Linus Torvalds @ 2017-07-09 21:37 UTC (permalink / raw)
To: Cong Wang
Cc: Network Development, Linux Kernel Mailing List, Gene Blue,
Andrew Morton, Manfred Spraul
On Sun, Jul 9, 2017 at 1:19 PM, Cong Wang <xiyou.wangcong@gmail.com> wrote:
>
> Setting 'sock' to NULL here should be sufficient to fix it.
Thanks. Applied and marked for stable.
Linus
^ permalink raw reply [flat|nested] 2+ messages in thread
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