rxrpc: Fix bundle counting for exclusive connections

Fix rxrpc_unbundle_conn() to not drop the bundle usage count when cleaning
up an exclusive connection.

Based on the suggested fix from Hillf Danton.

Fixes: 245500d853 ("rxrpc: Rewrite the client connection manager")
Reported-by: syzbot+d57aaf84dd8a550e6d91@syzkaller.appspotmail.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Hillf Danton <hdanton@sina.com>

net/rxrpc/conn_client.c

@@ -901,7 +901,7 @@ static void rxrpc_unbundle_conn(struct rxrpc_connection *conn)
 	struct rxrpc_bundle *bundle = conn->bundle;
 	struct rxrpc_local *local = bundle->params.local;
 	unsigned int bindex;
-	bool need_drop = false;
+	bool need_drop = false, need_put = false;
 	int i;
 
 	_enter("C=%x", conn->debug_id);
@@ -928,10 +928,11 @@ static void rxrpc_unbundle_conn(struct rxrpc_connection *conn)
 		if (i == ARRAY_SIZE(bundle->conns) && !bundle->params.exclusive) {
 			_debug("erase bundle");
 			rb_erase(&bundle->local_node, &local->client_bundles);
+			need_put = true;
 		}
 
 		spin_unlock(&local->client_bundles_lock);
-		if (i == ARRAY_SIZE(bundle->conns))
+		if (need_put)
 			rxrpc_put_bundle(bundle);
 	}