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

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

[David Vrabel]

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>
---
 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;
-- 
1.7.10.4

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

[Boris Ostrovsky]

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@citrix.com>


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


> ---
>   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;

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

[David Miller]

From: David Vrabel <david.vrabel@citrix.com>
Date: Wed, 27 May 2015 15:46:10 +0100

> 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>

Applied, thanks David.