virtio-net: drop NETIF_F_FRAGLIST

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 <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
static struct sk_buff *receive_big(struct net_device *dev,
				   struct virtnet_info *vi,
				   struct receive_queue *rq,
				   void *buf,
				   unsigned int len)
{
	struct page *page = buf;
	struct sk_buff *skb = page_to_skb(vi, rq, page, 0, len, PAGE_SIZE);

	if (unlikely(!skb))
		goto err;

	return skb;

err:
	dev->stats.rx_dropped++;
	give_pages(rq, page);
	return NULL;
}

static struct sk_buff *receive_big(struct net_device *dev,
				   struct virtnet_info *vi,
				   struct receive_queue *rq,
				   void *buf,
				   unsigned int len)
{
	struct page *page = buf;
	struct sk_buff *skb = page_to_skb(vi, rq, page, 0, len, PAGE_SIZE);

	if (unlikely(!skb))
		goto err;

	return skb;

err:
	dev->stats.rx_dropped++;
	give_pages(rq, page);
	return NULL;
}
