[PATCH 3.16.y-ckt 120/129] af_unix: fix struct pid memory leak

[Luis Henriques]

3.16.7-ckt25 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Eric Dumazet <edumazet at google.com>

commit fa0dc04df259ba2df3ce1920e9690c7842f8fa4b upstream.

Dmitry reported a struct pid leak detected by a syzkaller program.

Bug happens in unix_stream_recvmsg() when we break the loop when a
signal is pending, without properly releasing scm.

Fixes: b3ca9b02b007 ("net: fix multithreaded signal handling in unix recv routines")
Reported-by: Dmitry Vyukov <dvyukov at google.com>
Signed-off-by: Eric Dumazet <edumazet at google.com>
Cc: Rainer Weikusat <rweikusat at mobileactivedefense.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
[ luis: backported to 3.16:
  - use siocb->scm instead of &scm ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/unix/af_unix.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 20d752634efb..8ea231735292 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2155,6 +2155,7 @@ again:
 
 			if (signal_pending(current)) {
 				err = sock_intr_errno(timeo);
+				scm_destroy(siocb->scm);
 				goto out;
 			}