net: hisilicon: Fix potential use-after-free in hisi_femac_rx()

The skb is delivered to napi_gro_receive() which may free it, after
calling this, dereferencing skb may trigger use-after-free.

Fixes: 542ae60a ("net: hisilicon: Add Fast Ethernet MAC driver")
Signed-off-by: Liu Jian <liujian56@huawei.com>
Link: https://lore.kernel.org/r/20221203094240.1240211-1-liujian56@huawei.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/hisilicon/hisi_femac.c

@@ -283,7 +283,7 @@ static int hisi_femac_rx(struct net_device *dev, int limit)
 		skb->protocol = eth_type_trans(skb, dev);
 		napi_gro_receive(&priv->napi, skb);
 		dev->stats.rx_packets++;
-		dev->stats.rx_bytes += skb->len;
+		dev->stats.rx_bytes += len;
 next:
 		pos = (pos + 1) % rxq->num;
 		if (rx_pkts_num >= limit)