AX.25: Close socket connection on session completion

A socket connection made in ax.25 is not closed when session is
completed.  The heartbeat timer is stopped prematurely and this is
where the socket gets closed. Allow heatbeat timer to run to close
socket. Symptom occurs in kernels >= 4.2.0

Originally sent 6/15/2016. Resend with distribution list matching
scripts/maintainer.pl output.

Signed-off-by: Basil Gunn <basil@pacabunga.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ax25/af_ax25.c

@@ -976,7 +976,8 @@ static int ax25_release(struct socket *sock)
 			release_sock(sk);
 			ax25_disconnect(ax25, 0);
 			lock_sock(sk);
-			ax25_destroy_socket(ax25);
+			if (!sock_flag(ax25->sk, SOCK_DESTROY))
+				ax25_destroy_socket(ax25);
 			break;
 
 		case AX25_STATE_3:

net/ax25/ax25_ds_timer.c

@@ -102,6 +102,7 @@ void ax25_ds_heartbeat_expiry(ax25_cb *ax25)
 	switch (ax25->state) {
 
 	case AX25_STATE_0:
+	case AX25_STATE_2:
 		/* Magic here: If we listen() and a new link dies before it
 		   is accepted() it isn't 'dead' so doesn't get removed. */
 		if (!sk || sock_flag(sk, SOCK_DESTROY) ||
@@ -111,6 +112,7 @@ void ax25_ds_heartbeat_expiry(ax25_cb *ax25)
 				sock_hold(sk);
 				ax25_destroy_socket(ax25);
 				bh_unlock_sock(sk);
+				/* Ungrab socket and destroy it */
 				sock_put(sk);
 			} else
 				ax25_destroy_socket(ax25);
@@ -213,7 +215,8 @@ void ax25_ds_t1_timeout(ax25_cb *ax25)
 	case AX25_STATE_2:
 		if (ax25->n2count == ax25->n2) {
 			ax25_send_control(ax25, AX25_DISC, AX25_POLLON, AX25_COMMAND);
-			ax25_disconnect(ax25, ETIMEDOUT);
+			if (!sock_flag(ax25->sk, SOCK_DESTROY))
+				ax25_disconnect(ax25, ETIMEDOUT);
 			return;
 		} else {
 			ax25->n2count++;

net/ax25/ax25_std_timer.c

@@ -38,6 +38,7 @@ void ax25_std_heartbeat_expiry(ax25_cb *ax25)
 
 	switch (ax25->state) {
 	case AX25_STATE_0:
+	case AX25_STATE_2:
 		/* Magic here: If we listen() and a new link dies before it
 		   is accepted() it isn't 'dead' so doesn't get removed. */
 		if (!sk || sock_flag(sk, SOCK_DESTROY) ||
@@ -47,6 +48,7 @@ void ax25_std_heartbeat_expiry(ax25_cb *ax25)
 				sock_hold(sk);
 				ax25_destroy_socket(ax25);
 				bh_unlock_sock(sk);
+				/* Ungrab socket and destroy it */
 				sock_put(sk);
 			} else
 				ax25_destroy_socket(ax25);
@@ -144,7 +146,8 @@ void ax25_std_t1timer_expiry(ax25_cb *ax25)
 	case AX25_STATE_2:
 		if (ax25->n2count == ax25->n2) {
 			ax25_send_control(ax25, AX25_DISC, AX25_POLLON, AX25_COMMAND);
-			ax25_disconnect(ax25, ETIMEDOUT);
+			if (!sock_flag(ax25->sk, SOCK_DESTROY))
+				ax25_disconnect(ax25, ETIMEDOUT);
 			return;
 		} else {
 			ax25->n2count++;

net/ax25/ax25_subr.c

@@ -264,7 +264,8 @@ void ax25_disconnect(ax25_cb *ax25, int reason)
 {
 	ax25_clear_queues(ax25);
 
-	ax25_stop_heartbeat(ax25);
+	if (!sock_flag(ax25->sk, SOCK_DESTROY))
+		ax25_stop_heartbeat(ax25);
 	ax25_stop_t1timer(ax25);
 	ax25_stop_t2timer(ax25);
 	ax25_stop_t3timer(ax25);