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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Marek Lindner <mareklindner@neomailbox.ch>,
        Sven Eckelmann <sven@narfation.org>,
        Simon Wunderlich <sw@simonwunderlich.de>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.9 08/35] batman-adv: fix backbone_gw refcount on queue_work() failure
Date:   Thu, 18 Oct 2018 19:54:37 +0200
Message-Id: <20181018175423.682379090@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marek Lindner <mareklindner@neomailbox.ch>

[ Upstream commit 5af96b9c59c72fb2af2d19c5cc2f3cdcee391dff ]

The backbone_gw 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/bridge_loop_avoidance.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

--- a/net/batman-adv/bridge_loop_avoidance.c
+++ b/net/batman-adv/bridge_loop_avoidance.c
@@ -1767,6 +1767,7 @@ batadv_bla_loopdetect_check(struct batad
 {
 	struct batadv_bla_backbone_gw *backbone_gw;
 	struct ethhdr *ethhdr;
+	bool ret;
 
 	ethhdr = eth_hdr(skb);
 
@@ -1790,8 +1791,13 @@ batadv_bla_loopdetect_check(struct batad
 	if (unlikely(!backbone_gw))
 		return true;
 
-	queue_work(batadv_event_workqueue, &backbone_gw->report_work);
-	/* backbone_gw is unreferenced in the report work function function */
+	ret = queue_work(batadv_event_workqueue, &backbone_gw->report_work);
+
+	/* backbone_gw is unreferenced in the report work function function
+	 * if queue_work() call was successful
+	 */
+	if (!ret)
+		batadv_backbone_gw_put(backbone_gw);
 
 	return true;
 }