Patch "l2tp: ensure session can't get removed during pppol2tp_session_ioctl()" 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: ensure session can't get removed during pppol2tp_session_ioctl()

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-ensure-session-can-t-get-removed-during-pppol2tp_session_ioctl.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: Fri, 31 Mar 2017 13:02:26 +0200
Subject: l2tp: ensure session can't get removed during pppol2tp_session_ioctl()

From: Guillaume Nault <[email protected]>

commit 57377d63547861919ee634b845c7caa38de4a452 upstream.

Holding a reference on session is required before calling pppol2tp_session_ioctl(). The session could get freed while processing the ioctl otherwise. Since pppol2tp_session_ioctl() uses the session's socket, we also need to take a reference on it in l2tp_session_get().

---
 net/l2tp/l2tp_ppp.c |   15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

@@ -1141,11 +1141,18 @@ static int pppol2tp_tunnel_ioctl(struct
 		if (stats.session_id != 0) {
 			/* resend to session ioctl handler */
 			struct l2tp_session *session =
-				l2tp_session_find(sock_net(sk), tunnel, stats.session_id);
-			if (session != NULL)
-				err = pppol2tp_session_ioctl(session, cmd, arg);
-			else
+				l2tp_session_get(sock_net(sk), tunnel,
+						 stats.session_id, true);
+
+			if (session) {
+				err = pppol2tp_session_ioctl(session, cmd,
+							     arg);
+				if (session->deref)
+					session->deref(session);
+				l2tp_session_dec_refcount(session);
+			} else {
 				err = -EBADR;
+			}
 			break;
 		}
 #ifdef CONFIG_XFRM

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

queue-4.9/l2tp-take-a-reference-on-sessions-used-in-genetlink-handlers.patch queue-4.9/l2tp-ensure-session-can-t-get-removed-during-pppol2tp_session_ioctl.patch queue-4.9/l2tp-fix-race-in-l2tp_recv_common.patch queue-4.9/l2tp-hold-session-while-sending-creation-notifications.patch queue-4.9/l2tp-fix-duplicate-session-creation.patch