# Re: \[PATCH net\] virtio-net: drop NETIF\_F\_FRAGLIST

- From: Michael S. Tsirkin \<mst@redhat.com\>
- Date: 2015-08-04 10:05:39 
- List: virtualization
- Page: https://ratatoskr.run/virtualization/2015/08/4550303
- Thread: https://ratatoskr.run/netdev/2015/08/4550299/t.md

```text
On Tue, Aug 04, 2015 at 05:55:45PM +0800, Jason Wang wrote:
> virtio declares support for NETIF_F_FRAGLIST, but assumes
> that there are at most MAX_SKB_FRAGS + 2 fragments which isn't
> always true with a fraglist.
> 
> A longer fraglist in the skb will make the call to skb_to_sgvec overflow
> the sg array, leading to memory corruption.
> 
> Drop NETIF_F_FRAGLIST so we only get what we can handle.
> 
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Jason Wang <redacted>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

Especially important now that virtio_net: add gro capability
was merged for net-next, making bridged setups create fraglists.

> ---
> The patch is needed for stable.
> ---
>  drivers/net/virtio_net.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 7fbca37..2347a73 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1756,9 +1756,9 @@ static int virtnet_probe(struct virtio_device *vdev)
>  	/* Do we support "hardware" checksums? */
>  	if (virtio_has_feature(vdev, VIRTIO_NET_F_CSUM)) {
>  		/* This opens up the world of extra features. */
> -		dev->hw_features |= NETIF_F_HW_CSUM|NETIF_F_SG|NETIF_F_FRAGLIST;
> +		dev->hw_features |= NETIF_F_HW_CSUM|NETIF_F_SG;
>  		if (csum)
> -			dev->features |= NETIF_F_HW_CSUM|NETIF_F_SG|NETIF_F_FRAGLIST;
> +			dev->features |= NETIF_F_HW_CSUM|NETIF_F_SG;
>  
>  		if (virtio_has_feature(vdev, VIRTIO_NET_F_GSO)) {
>  			dev->hw_features |= NETIF_F_TSO | NETIF_F_UFO
> -- 
> 2.1.4
```