From d6cb3b8de682564c86b09c56e43162e873769d0e Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Sun, 9 Jul 2017 13:19:55 -0700 Subject: [PATCH] mqueue: fix a use-after-free in sys_mq_notify() 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 Signed-off-by: Cong Wang Cc: Andrew Morton Cc: Manfred Spraul Cc: stable@kernel.org Signed-off-by: Linus Torvalds (cherry picked from commit f991af3daabaecff34684fd51fac80319d1baad1) Orabug: 26584960 CVE: CVE-2017-11176 Signed-off-by: Tim Tianyang Chen Reviewed-by: Jack Vogel --- ipc/mqueue.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/ipc/mqueue.c b/ipc/mqueue.c index c3fc5c2b63f3..e4e8b6080b33 100644 --- a/ipc/mqueue.c +++ b/ipc/mqueue.c @@ -1239,8 +1239,10 @@ retry: 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; -- 2.50.1