sctp: Disallow new connection on a closing socket

If a socket has a lot of association that are in the process of
of being closed/aborted, it is possible for a remote to establish
new associations during the time period that the old ones are shutting
down.  If this was a result of a close() call, there will be no socket
and will cause a memory leak.  We'll prevent this by setting the
socket state to CLOSING and disallow new associations when in this state.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>

net/sctp/socket.c

@@ -1361,6 +1361,7 @@ SCTP_STATIC void sctp_close(struct sock *sk, long timeout)
 
 	sctp_lock_sock(sk);
 	sk->sk_shutdown = SHUTDOWN_MASK;
+	sk->sk_state = SCTP_SS_CLOSING;
 
 	ep = sctp_sk(sk)->ep;