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>

include/net/sctp/constants.h

@@ -231,7 +231,7 @@ typedef enum {
 	SCTP_SS_LISTENING      = TCP_LISTEN,
 	SCTP_SS_ESTABLISHING   = TCP_SYN_SENT,
 	SCTP_SS_ESTABLISHED    = TCP_ESTABLISHED,
-	SCTP_SS_DISCONNECTING  = TCP_CLOSING,
+	SCTP_SS_CLOSING        = TCP_CLOSING,
 } sctp_sock_state_t;
 
 /* These functions map various type to printable names.  */

net/sctp/sm_statefuns.c

@@ -334,6 +334,15 @@ sctp_disposition_t sctp_sf_do_5_1B_init(const struct sctp_endpoint *ep,
 	if (!sctp_chunk_length_valid(chunk, sizeof(sctp_init_chunk_t)))
 		return sctp_sf_pdiscard(ep, asoc, type, arg, commands);
 
+	/* If the INIT is coming toward a closing socket, we'll send back
+	 * and ABORT.  Essentially, this catches the race of INIT being
+	 * backloged to the socket at the same time as the user isses close().
+	 * Since the socket and all its associations are going away, we
+	 * can treat this OOTB
+	 */
+	if (sctp_sstate(ep->base.sk, CLOSING))
+		return sctp_sf_tabort_8_4_8(ep, asoc, type, arg, commands);
+
 	/* Verify the INIT chunk before processing it. */
 	err_chunk = NULL;
 	if (!sctp_verify_init(asoc, chunk->chunk_hdr->type,

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;