net: Fix soft lockups/OOM issues w/ unix garbage collector

This is an implementation of David Miller's suggested fix in:
  https://bugzilla.redhat.com/show_bug.cgi?id=470201

It has been updated to use wait_event() instead of
wait_event_interruptible().

Paraphrasing the description from the above report, it makes sendmsg()
block while UNIX garbage collection is in progress. This avoids a
situation where child processes continue to queue new FDs over a
AF_UNIX socket to a parent which is in the exit path and running
garbage collection on these FDs. This contention can result in soft
lockups and oom-killing of unrelated processes.

Signed-off-by: dann frazier <dannf@hp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index eb90f77bb0e2..66d5ac4773ab 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1343,6 +1343,7 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
 
         if (NULL == siocb->scm)
                 siocb->scm = &tmp_scm;
+        wait_for_unix_gc();
         err = scm_send(sock, msg, siocb->scm);
         if (err < 0)
                 return err;
@@ -1493,6 +1494,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
 
         if (NULL == siocb->scm)
                 siocb->scm = &tmp_scm;
+        wait_for_unix_gc();
         err = scm_send(sock, msg, siocb->scm);
         if (err < 0)
                 return err;