virtio-net: free bufs correctly on invalid packet length

When a packet with invalid length arrives, ensure that the packet
is freed correctly if mergeable packet buffers and big packets
(GUEST_TSO4) are both enabled.

Signed-off-by: Michael Dalton <mwdalton@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Acked-by: Andrew Vagin <avagin@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/virtio_net.c

@@ -426,10 +426,10 @@ static void receive_buf(struct receive_queue *rq, void *buf, unsigned int len)
 	if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
 		pr_debug("%s: short packet %i\n", dev->name, len);
 		dev->stats.rx_length_errors++;
-		if (vi->big_packets)
-			give_pages(rq, buf);
-		else if (vi->mergeable_rx_bufs)
+		if (vi->mergeable_rx_bufs)
 			put_page(virt_to_head_page(buf));
+		else if (vi->big_packets)
+			give_pages(rq, buf);
 		else
 			dev_kfree_skb(buf);
 		return;