xen-netfront: properly destroy queues when removing device

xennet_remove() freed the queues before freeing the netdevice which
results in a use-after-free when free_netdev() tries to delete the
napi instances that have already been freed.

Fix this by fully destroy the queues (which includes deleting the napi
instances) before freeing the netdevice.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 13 deletions

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 3f45afd4382e..e031c943286e 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1698,6 +1698,7 @@ static void xennet_destroy_queues(struct netfront_info *info)
 
                 if (netif_running(info->netdev))
                         napi_disable(&queue->napi);
+                del_timer_sync(&queue->rx_refill_timer);
                 netif_napi_del(&queue->napi);
         }
 
@@ -2102,9 +2103,6 @@ static const struct attribute_group xennet_dev_group = {
 static int xennet_remove(struct xenbus_device *dev)
 {
         struct netfront_info *info = dev_get_drvdata(&dev->dev);
-        unsigned int num_queues = info->netdev->real_num_tx_queues;
-        struct netfront_queue *queue = NULL;
-        unsigned int i = 0;
 
         dev_dbg(&dev->dev, "%s\n", dev->nodename);
 
@@ -2112,16 +2110,7 @@ static int xennet_remove(struct xenbus_device *dev)
 
         unregister_netdev(info->netdev);
 
-        for (i = 0; i < num_queues; ++i) {
-                queue = &info->queues[i];
-                del_timer_sync(&queue->rx_refill_timer);
-        }
-
-        if (num_queues) {
-                kfree(info->queues);
-                info->queues = NULL;
-        }
-
+        xennet_destroy_queues(info);
         xennet_free_netdev(info->netdev);
 
         return 0;