| From: Cong Wang <xiyou.wangcong@gmail.com> |
| Date: Sun, 9 Jul 2017 13:19:55 -0700 |
| Subject: [PATCH] mqueue: fix a use-after-free in sys_mq_notify() |
| References: bnc#1060662 |
| Patch-mainline: v4.12.2 |
| Git-commit: f991af3daabaecff34684fd51fac80319d1baad1 |
| |
| 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@gmail.com> |
| Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> |
| Cc: Andrew Morton <akpm@linux-foundation.org> |
| Cc: Manfred Spraul <manfred@colorfullife.com> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| Signed-off-by: Jiri Slaby <jslaby@suse.cz> |
| |
| ipc/mqueue.c | 4 +++- |
| 1 file changed, 3 insertions(+), 1 deletion(-) |
| |
| diff --git a/ipc/mqueue.c b/ipc/mqueue.c |
| index e8d41ff57241..a6ced9e07e1c 100644 |
| |
| |
| @@ -1253,8 +1253,10 @@ 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; |
| -- |
| 2.14.2 |
| |