3.16.47-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Cong Wang <[email protected]> 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 <[email protected]> Signed-off-by: Cong Wang <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Manfred Spraul <[email protected]> Cc: [email protected] Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Ben Hutchings <[email protected]> --- 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;
