Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1683836

[Patch v2] mqueue: fix a use-after-free in sys_mq_notify()

Show all headers | View raw

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

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

[Patch v2] mqueue: fix a use-after-free in sys_mq_notify() Cong Wang <xiyou.wangcong@gmail.com> - 2017-07-09 22:30 +0200
  Re: [Patch v2] mqueue: fix a use-after-free in sys_mq_notify() Linus Torvalds <torvalds@linux-foundation.org> - 2017-07-09 23:40 +0200

csiph-web