Patch "sctp: change sk state only when it has assocs in sctp_shutdown" has been added to the 4.8-stable tree

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

    sctp: change sk state only when it has assocs in sctp_shutdown

to the 4.8-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:
     sctp-change-sk-state-only-when-it-has-assocs-in-sctp_shutdown.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let [off-list ref] know about it.

From foo@baz Fri Nov 18 11:35:46 CET 2016

From: Xin Long <lucien.xin@gmail.com>
Date: Sun, 13 Nov 2016 21:44:37 +0800
Subject: sctp: change sk state only when it has assocs in sctp_shutdown

From: Xin Long <lucien.xin@gmail.com>


[ Upstream commit 5bf35ddfee052d44f39ebaa395d87101c8918405 ]

Now when users shutdown a sock with SEND_SHUTDOWN in sctp, even if
this sock has no connection (assoc), sk state would be changed to
SCTP_SS_CLOSING, which is not as we expect.

Besides, after that if users try to listen on this sock, kernel
could even panic when it dereference sctp_sk(sk)->bind_hash in
sctp_inet_listen, as bind_hash is null when sock has no assoc.

This patch is to move sk state change after checking sk assocs
is not empty, and also merge these two if() conditions and reduce
indent level.

Fixes: d46e416c11c8 ("sctp: sctp should change socket state when shutdown is received")
Reported-by: Andrey Konovalov <redacted>
Tested-by: Andrey Konovalov <redacted>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/sctp/socket.c |   15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c

@@ -4281,19 +4281,18 @@ static void sctp_shutdown(struct sock *s
 {
 	struct net *net = sock_net(sk);
 	struct sctp_endpoint *ep;
-	struct sctp_association *asoc;
 
 	if (!sctp_style(sk, TCP))
 		return;
 
-	if (how & SEND_SHUTDOWN) {
+	ep = sctp_sk(sk)->ep;
+	if (how & SEND_SHUTDOWN && !list_empty(&ep->asocs)) {
+		struct sctp_association *asoc;
+
 		sk->sk_state = SCTP_SS_CLOSING;
-		ep = sctp_sk(sk)->ep;
-		if (!list_empty(&ep->asocs)) {
-			asoc = list_entry(ep->asocs.next,
-					  struct sctp_association, asocs);
-			sctp_primitive_SHUTDOWN(net, asoc, NULL);
-		}
+		asoc = list_entry(ep->asocs.next,
+				  struct sctp_association, asocs);
+		sctp_primitive_SHUTDOWN(net, asoc, NULL);
 	}
 }
 

Patches currently in stable-queue which might be from lucien.xin@gmail.com are

queue-4.8/sctp-assign-assoc_id-earlier-in-__sctp_connect.patch
queue-4.8/sctp-change-sk-state-only-when-it-has-assocs-in-sctp_shutdown.patch