batman-adv: fix hardif_neigh refcount on queue_work() failure

[ Upstream commit 4c4af690 ]

The hardif_neigh refcounter is to be decreased by the queued work and
currently is never decreased if the queue_work() call fails.
Fix by checking the queue_work() return value and decrease refcount
if necessary.
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/batman-adv/bat_v_elp.c

@@ -254,6 +254,7 @@ static void batadv_v_elp_periodic_work(struct work_struct *work)
 	struct batadv_priv *bat_priv;
 	struct sk_buff *skb;
 	u32 elp_interval;
+	bool ret;
 
 	bat_v = container_of(work, struct batadv_hard_iface_bat_v, elp_wq.work);
 	hard_iface = container_of(bat_v, struct batadv_hard_iface, bat_v);
@@ -315,8 +316,11 @@ static void batadv_v_elp_periodic_work(struct work_struct *work)
 		 * may sleep and that is not allowed in an rcu protected
 		 * context. Therefore schedule a task for that.
 		 */
-		queue_work(batadv_event_workqueue,
+		ret = queue_work(batadv_event_workqueue,
 				 &hardif_neigh->bat_v.metric_work);
+
+		if (!ret)
+			batadv_hardif_neigh_put(hardif_neigh);
 	}
 	rcu_read_unlock();