Messages in this thread Patch in this message | | | From | Ben Hutchings <> | Date | Fri, 18 Aug 2017 14:13:13 +0100 | Subject | [PATCH 3.2 58/59] mqueue: fix a use-after-free in sys_mq_notify() |
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3.2.92-rc1 review patch. If anyone has any objections, please let me know.
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From: Cong Wang <xiyou.wangcong@gmail.com>
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> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- ipc/mqueue.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/ipc/mqueue.c +++ b/ipc/mqueue.c @@ -1095,8 +1095,10 @@ 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;
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