net: lantiq_xrx200: fix use after free bug

The skb->len field is read after the packet is sent to the network
stack. In the meantime, skb can be freed. This patch fixes this bug.

Fixes: c3e6b2c3 ("net: lantiq_xrx200: add ingress SG DMA support")
Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Aleksander Jan Bajkowski <olek2@wp.pl>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/lantiq_xrx200.c

@@ -260,9 +260,9 @@ static int xrx200_hw_receive(struct xrx200_chan *ch)
 
 	if (ctl & LTQ_DMA_EOP) {
 		ch->skb_head->protocol = eth_type_trans(ch->skb_head, net_dev);
-		netif_receive_skb(ch->skb_head);
 		net_dev->stats.rx_packets++;
 		net_dev->stats.rx_bytes += ch->skb_head->len;
+		netif_receive_skb(ch->skb_head);
 		ch->skb_head = NULL;
 		ch->skb_tail = NULL;
 		ret = XRX200_DMA_PACKET_COMPLETE;