tipc: drop subscriber connection id invalidation

When a topology server subscriber is disconnected, the associated
connection id is set to zero. A check vs zero is then done in the
subscription timeout function to see if the subscriber have been
shut down. This is unnecessary, because all subscription timers
will be cancelled when a subscriber terminates. Setting the
connection id to zero is actually harmful because id zero is the
identity of the topology server listening socket, and can cause a
race that leads to this socket being closed instead.

Signed-off-by: Erik Hugne <erik.hugne@ericsson.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/subscr.c

@@ -149,14 +149,6 @@ static void subscr_timeout(struct tipc_subscription *sub)
 	/* The spin lock per subscriber is used to protect its members */
 	spin_lock_bh(&subscriber->lock);
 
-	/* Validate if the connection related to the subscriber is
-	 * closed (in case subscriber is terminating)
-	 */
-	if (subscriber->conid == 0) {
-		spin_unlock_bh(&subscriber->lock);
-		return;
-	}
-
 	/* Validate timeout (in case subscription is being cancelled) */
 	if (sub->timeout == TIPC_WAIT_FOREVER) {
 		spin_unlock_bh(&subscriber->lock);
@@ -211,9 +203,6 @@ static void subscr_release(struct tipc_subscriber *subscriber)
 
 	spin_lock_bh(&subscriber->lock);
 
-	/* Invalidate subscriber reference */
-	subscriber->conid = 0;
-
 	/* Destroy any existing subscriptions for subscriber */
 	list_for_each_entry_safe(sub, sub_temp, &subscriber->subscription_list,
 				 subscription_list) {