Patch "l2tp: purge socket queues in the .destruct() callback" has been added to the 4.9-stable tree

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

l2tp: purge socket queues in the .destruct() callback

to the 4.9-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:
l2tp-purge-socket-queues-in-the-.destruct-callback.patch
and it can be found in the queue-4.9 subdirectory.

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

From: Guillaume Nault <[email protected]>
Date: Wed, 29 Mar 2017 08:45:29 +0200
Subject: l2tp: purge socket queues in the .destruct() callback

From: Guillaume Nault <[email protected]>

[ Upstream commit e91793bb615cf6cdd59c0b6749fe173687bb0947 ]

The Rx path may grab the socket right before pppol2tp_release(), but nothing guarantees that it will enqueue packets before skb_queue_purge(). Therefore, the socket can be destroyed without its queues fully purged.

Fix this by purging queues in pppol2tp_session_destruct() where we're guaranteed nothing is still referencing the socket.

---
 net/l2tp/l2tp_ppp.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

@@ -450,6 +450,10 @@ static void pppol2tp_session_close(struc
 static void pppol2tp_session_destruct(struct sock *sk)
 {
 	struct l2tp_session *session = sk->sk_user_data;
+
+	skb_queue_purge(&sk->sk_receive_queue);
+	skb_queue_purge(&sk->sk_write_queue);
+
 	if (session) {
 		sk->sk_user_data = NULL;
 		BUG_ON(session->magic != L2TP_SESSION_MAGIC);

@@ -488,9 +492,6 @@ static int pppol2tp_release(struct socke
 		l2tp_session_queue_purge(session);
 		sock_put(sk);
 	}
-	skb_queue_purge(&sk->sk_receive_queue);
-	skb_queue_purge(&sk->sk_write_queue);
-
 	release_sock(sk);
 
 	/* This will delete the session context via

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

queue-4.9/l2tp-purge-socket-queues-in-the-.destruct-callback.patch queue-4.9/l2tp-hold-tunnel-socket-when-handling-control-frames-in-l2tp_ip-and-l2tp_ip6.patch queue-4.9/l2tp-take-reference-on-sessions-being-dumped.patch queue-4.9/l2tp-fix-ppp-pseudo-wire-auto-loading.patch