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

[<gregkh@linuxfoundation.org>]

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 <stable@vger.kernel.org> know about it.


>From foo@baz Sat Apr 29 08:22:13 CEST 2017
From: Guillaume Nault <g.nault@alphalink.fr>
Date: Wed, 29 Mar 2017 08:45:29 +0200
Subject: l2tp: purge socket queues in the .destruct() callback

From: Guillaume Nault <g.nault@alphalink.fr>


[ 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.

Fixes: 9e9cb6221aa7 ("l2tp: fix userspace reception on plain L2TP sockets")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/l2tp/l2tp_ppp.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -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 g.nault@alphalink.fr 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