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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Chas Williams" <3chas3@gmail.com>,
        "David S. Miller" <davem@davemloft.net>
Date:   Sun, 11 Nov 2018 19:49:05 +0000
Message-ID: <lsq.1541965745.254874524@decadent.org.uk>
Subject: [PATCH 3.16 169/366] net/xen-netfront: only clean up queues if
 present
In-Reply-To: <lsq.1541965744.387173642@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Chas Williams <3chas3@gmail.com>

commit 9a873c71e91cabf4c10fd9bbd8358c22deaf6c9e upstream.

If you simply load and unload the module without starting the interfaces,
the queues are never created and you get a bad pointer dereference.

Signed-off-by: Chas Williams <3chas3@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/net/xen-netfront.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1422,7 +1422,7 @@ static void xennet_disconnect_backend(st
 
 	netif_carrier_off(info->netdev);
 
-	for (i = 0; i < num_queues; ++i) {
+	for (i = 0; i < num_queues && info->queues; ++i) {
 		struct netfront_queue *queue = &info->queues[i];
 
 		del_timer_sync(&queue->rx_refill_timer);
@@ -2294,7 +2294,8 @@ static int xennet_remove(struct xenbus_d
 
 	unregister_netdev(info->netdev);
 
-	xennet_destroy_queues(info);
+	if (info->queues)
+		xennet_destroy_queues(info);
 	xennet_free_netdev(info->netdev);
 
 	return 0;