staging: fsl-dpaa2/eth: Fix skb use after free

Once a Tx frame descriptor is enqueued, an interrupt might be triggered
to process the Tx confirmation and free the skb, hitting a memory use
after free when updating the tx_bytes statistic based on skb->len.

Use the frame descriptor length instead.
Signed-off-by: Bogdan Purcareata <bogdan.purcareata@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fsl-dpaa2/ethernet/dpaa2-eth.c

@@ -616,7 +616,7 @@ static netdev_tx_t dpaa2_eth_tx(struct sk_buff *skb, struct net_device *net_dev)
 		free_tx_fd(priv, &fd, NULL);
 	} else {
 		percpu_stats->tx_packets++;
-		percpu_stats->tx_bytes += skb->len;
+		percpu_stats->tx_bytes += dpaa2_fd_get_len(&fd);
 	}
 
 	return NETDEV_TX_OK;