sfc: fix race in efx_enqueue_skb_tso()

As soon as skb is pushed to hardware, it can be completed and freed, so
we should not dereference skb anymore.
Signed-off-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/tx.c

@@ -1173,11 +1173,11 @@ static int efx_enqueue_skb_tso(struct efx_tx_queue *tx_queue,
 			goto mem_err;
 	}
 
+	netdev_tx_sent_queue(tx_queue->core_txq, skb->len);
+
 	/* Pass off to hardware */
 	efx_nic_push_buffers(tx_queue);
 
-	netdev_tx_sent_queue(tx_queue->core_txq, skb->len);
-
 	tx_queue->tso_bursts++;
 	return NETDEV_TX_OK;