tg3: Fix race condition in tg3_get_stats64()

commit 0f566b20 upstream.

Spinlock should be taken before checking for tp->hw_stats.
Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/net/ethernet/broadcom/tg3.c

@@ -12282,10 +12282,12 @@ static struct rtnl_link_stats64 *tg3_get_stats64(struct net_device *dev,
 {
 	struct tg3 *tp = netdev_priv(dev);
 
-	if (!tp->hw_stats)
+	spin_lock_bh(&tp->lock);
+	if (!tp->hw_stats) {
+		spin_unlock_bh(&tp->lock);
 		return &tp->net_stats_prev;
+	}
 
-	spin_lock_bh(&tp->lock);
 	tg3_get_nstats(tp, stats);
 	spin_unlock_bh(&tp->lock);