xen-netback: free queues after freeing the net device

If a queue still has a NAPI instance added to the net device, freeing
the queues early results in a use-after-free.

The shouldn't ever happen because we disconnect and tear down all queues
before freeing the net device, but doing this makes it obviously safe.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 11 deletions

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 3bba6ceee132..f5231a2dd2ac 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -685,22 +685,16 @@ void xenvif_deinit_queue(struct xenvif_queue *queue)
 
 void xenvif_free(struct xenvif *vif)
 {
-        struct xenvif_queue *queue = NULL;
+        struct xenvif_queue *queues = vif->queues;
         unsigned int num_queues = vif->num_queues;
         unsigned int queue_index;
 
         unregister_netdev(vif->dev);
-
-        for (queue_index = 0; queue_index < num_queues; ++queue_index) {
-                queue = &vif->queues[queue_index];
-                xenvif_deinit_queue(queue);
-        }
-
-        vfree(vif->queues);
-        vif->queues = NULL;
-        vif->num_queues = 0;
-
         free_netdev(vif->dev);
 
+        for (queue_index = 0; queue_index < num_queues; ++queue_index)
+                xenvif_deinit_queue(&queues[queue_index]);
+        vfree(queues);
+
         module_put(THIS_MODULE);
 }