From 485bc0f0d20494eb7a5302e8ece2535a8912b16f Mon Sep 17 00:00:00 2001
From: Xin Long <lucien.xin@gmail.com>
Date: Thu, 6 Apr 2017 13:10:52 +0800
Subject: [PATCH] sctp: listen on the sock only when it's state is listening or
 closed

commit 34b2789f1d9bf8dcca9b5cb553d076ca2cd898ee upstream.

Now sctp doesn't check sock's state before listening on it. It could
even cause changing a sock with any state to become a listening sock
when doing sctp_listen.

This patch is to fix it by checking sock's state in sctp_listen, so
that it will listen on the sock with right state.

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 3908dec4ad30..ecb1a27dfd3f 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -6852,6 +6852,9 @@ int sctp_inet_listen(struct socket *sock, int backlog)
 	if (sock->state != SS_UNCONNECTED)
 		goto out;
 
+	if (!sctp_sstate(sk, LISTENING) && !sctp_sstate(sk, CLOSED))
+		goto out;
+
 	/* If backlog is zero, disable listening. */
 	if (!backlog) {
 		if (sctp_sstate(sk, CLOSED))
-- 
2.12.0