From: Cong Wang <xiyou.wangcong@gmail.com>
To: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, geneblue.mail@gmail.com,
Cong Wang <xiyou.wangcong@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Manfred Spraul <manfred@colorfullife.com>
Subject: [Patch v2] mqueue: fix a use-after-free in sys_mq_notify()
Date: Sun, 9 Jul 2017 13:19:55 -0700 [thread overview]
Message-ID: <1499631595-12625-1-git-send-email-xiyou.wangcong@gmail.com> (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
next reply other threads:[~2017-07-09 20:20 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-09 20:19 Cong Wang [this message]
2017-07-09 21:37 ` [Patch v2] mqueue: fix a use-after-free in sys_mq_notify() Linus Torvalds
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