[PATCH 3.16 167/366] xen-netfront: properly destroy queues when removing device

Ben Hutchings
2018-11-11T20:36:51Z

From: David Vrabel <david.vrabel@citrix.com>

commit ad0681185770716523c81b156c44b9804d7b8ed2 upstream.

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>
[bwh: Backported to 3.16: I already backported most of this along with
the later commit 74470954857c "xen-netfront: Delete rx_refill_timer in
xennet_disconnect_backend()"; don't move the del_timer_sync() again.]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -2294,7 +2294,6 @@ static const struct xenbus_device_id net
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;

dev_dbg(&dev->dev, "%s\n", dev->nodename);

@@ -2302,11 +2301,7 @@ static int xennet_remove(struct xenbus_d

unregister_netdev(info->netdev);

- if (num_queues) {
- kfree(info->queues);
- info->queues = NULL;
- }
-
+ xennet_destroy_queues(info);
xennet_free_netdev(info->netdev);

return 0;