[PATCH 3.17 39/47] net: mvneta: fix race condition in mvneta_tx()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

3.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 5f478b41033606d325e420df693162e2524c2b94 ]

mvneta_tx() dereferences skb to get skb->len too late,
as hardware might have completed the transmit and TX completion
could have freed the skb from another cpu.

Fixes: 71f6d1b31fb1 ("net: mvneta: replace Tx timer with a real interrupt")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/ethernet/marvell/mvneta.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -1721,6 +1721,7 @@ static int mvneta_tx(struct sk_buff *skb
 	u16 txq_id = skb_get_queue_mapping(skb);
 	struct mvneta_tx_queue *txq = &pp->txqs[txq_id];
 	struct mvneta_tx_desc *tx_desc;
+	int len = skb->len;
 	int frags = 0;
 	u32 tx_cmd;
 
@@ -1788,7 +1789,7 @@ out:
 
 		u64_stats_update_begin(&stats->syncp);
 		stats->tx_packets++;
-		stats->tx_bytes  += skb->len;
+		stats->tx_bytes  += len;
 		u64_stats_update_end(&stats->syncp);
 	} else {
 		dev->stats.tx_dropped++;