Patch "af_unix: Guard against other == sk in unix_dgram_sendmsg" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

    af_unix: Guard against other == sk in unix_dgram_sendmsg

to the 4.4-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:
af_unix-guard-against-other-sk-in-unix_dgram_sendmsg.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Rainer Weikusat <[email protected]>
Date: Thu, 11 Feb 2016 19:37:27 +0000
Subject: af_unix: Guard against other == sk in unix_dgram_sendmsg

From: Rainer Weikusat <[email protected]>

[ Upstream commit a5527dda344fff0514b7989ef7a755729769daa1 ]

The unix_dgram_sendmsg routine use the following test

if (unlikely(unix_peer(other) != sk && unix_recvq_full(other))) {

to determine if sk and other are in an n:1 association (either established via connect or by using sendto to send messages to an unrelated socket identified by address). This isn't correct as the specified address could have been bound to the sending socket itself or because this socket could have been connected to itself by the time of the unix_peer_get but disconnected before the unix_state_lock(other). In both cases, the if-block would be entered despite other == sk which might either block the sender unintentionally or lead to trying to unlock the same spin lock twice for a non-blocking send. Add a other != sk check to guard against this.

---
 net/unix/af_unix.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

@@ -1781,7 +1781,12 @@ restart_locked:
 			goto out_unlock;
 	}
 
-	if (unlikely(unix_peer(other) != sk && unix_recvq_full(other))) {
+	/* other == sk && unix_peer(other) != sk if
+	 * - unix_peer(sk) == NULL, destination address bound to sk
+	 * - unix_peer(sk) == sk by time of get but disconnected before lock
+	 */
+	if (other != sk &&
+	    unlikely(unix_peer(other) != sk && unix_recvq_full(other))) {
 		if (timeo) {
 			timeo = unix_wait_for_peer(other, timeo);
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/af_unix-don-t-set-err-in-unix_stream_read_generic-unless-there-was-an-error.patch queue-4.4/af_unix-fix-struct-pid-memory-leak.patch queue-4.4/af_unix-guard-against-other-sk-in-unix_dgram_sendmsg.patch