This is a note to let you know that I've just added the patch titled mqueue: fix a use-after-free in sys_mq_notify() to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mqueue-fix-a-use-after-free-in-sys_mq_notify.patch and it can be found in the queue-3.18 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From f991af3daabaecff34684fd51fac80319d1baad1 Mon Sep 17 00:00:00 2001 From: Cong Wang <xiyou.wangcong@xxxxxxxxx> Date: Sun, 9 Jul 2017 13:19:55 -0700 Subject: mqueue: fix a use-after-free in sys_mq_notify() From: Cong Wang <xiyou.wangcong@xxxxxxxxx> commit f991af3daabaecff34684fd51fac80319d1baad1 upstream. 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@xxxxxxxxx> Signed-off-by: Cong Wang <xiyou.wangcong@xxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- ipc/mqueue.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- 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; Patches currently in stable-queue which might be from xiyou.wangcong@xxxxxxxxx are queue-3.18/mqueue-fix-a-use-after-free-in-sys_mq_notify.patch