be2net: fix a race in be_xmit()

[ Upstream commit cd8f76c0 ]

As soon as hardware is notified of a transmit, we no longer can assume
skb can be dereferenced, as TX completion might have freed the packet.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Sathya Perla <sathya.perla@emulex.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/net/ethernet/emulex/benet/be_main.c

@@ -696,6 +696,8 @@ static netdev_tx_t be_xmit(struct sk_buff *skb,
 
 	copied = make_tx_wrbs(adapter, txq, skb, wrb_cnt, dummy_wrb);
 	if (copied) {
+		int gso_segs = skb_shinfo(skb)->gso_segs;
+
 		/* record the sent skb in the sent_skb table */
 		BUG_ON(txo->sent_skb_list[start]);
 		txo->sent_skb_list[start] = skb;
@@ -713,8 +715,7 @@ static netdev_tx_t be_xmit(struct sk_buff *skb,
 
 		be_txq_notify(adapter, txq->id, wrb_cnt);
 
-		be_tx_stats_update(txo, wrb_cnt, copied,
-				skb_shinfo(skb)->gso_segs, stopped);
+		be_tx_stats_update(txo, wrb_cnt, copied, gso_segs, stopped);
 	} else {
 		txq->head = start;
 		dev_kfree_skb_any(skb);