virtio-net: correctly transmit XDP buff after linearizing

[ Upstream commit 5d458a1 ]

We should not go for the error path after successfully transmitting a
XDP buffer after linearizing. Since the error path may try to pop and
drop next packet and increase the drop counters. Fixing this by simply
drop the refcnt of original page and go for xmit path.

Fixes: 72979a6 ("virtio_net: xdp, add slowpath case for non contiguous buffers")
Cc: John Fastabend <john.fastabend@gmail.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/virtio_net.c

@@ -688,7 +688,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 				trace_xdp_exception(vi->dev, xdp_prog, act);
 			ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);
 			if (unlikely(xdp_page != page))
-				goto err_xdp;
+				put_page(page);
 			rcu_read_unlock();
 			goto xdp_xmit;
 		default: