Re: [Xen-devel] [PATCHv1] xen-netfront: properly destroy queues when removing device

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 05/27/2015 10:46 AM, David Vrabel wrote:
> 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@xxxxxxxxxx>

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>


> ---
>   drivers/net/xen-netfront.c |   15 ++-------------
>   1 file changed, 2 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index 3f45afd..e031c94 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;

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