igb: fix race conditions on queuing skb for HW time stamp

igb has a single set of TX time stamping resources per NIC.
Use a simple bit lock to avoid race conditions and leaking skbs
when multiple TX rings try to claim time stamping.
Signed-off-by: Jakub Kicinski <kubakici@wp.pl>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/igb/igb.h

@@ -492,7 +492,8 @@ struct igb_adapter {
 enum e1000_state_t {
 	__IGB_TESTING,
 	__IGB_RESETTING,
-	__IGB_DOWN
+	__IGB_DOWN,
+	__IGB_PTP_TX_IN_PROGRESS,
 };
 
 enum igb_boards {

drivers/net/ethernet/intel/igb/igb_main.c

@@ -4983,7 +4983,8 @@ netdev_tx_t igb_xmit_frame_ring(struct sk_buff *skb,
 	if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)) {
 		struct igb_adapter *adapter = netdev_priv(tx_ring->netdev);
 
-		if (!(adapter->ptp_tx_skb)) {
+		if (!test_and_set_bit_lock(__IGB_PTP_TX_IN_PROGRESS,
+					   &adapter->state)) {
 			skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
 			tx_flags |= IGB_TX_FLAGS_TSTAMP;
 

drivers/net/ethernet/intel/igb/igb_ptp.c

@@ -387,6 +387,7 @@ static void igb_ptp_tx_work(struct work_struct *work)
 				   IGB_PTP_TX_TIMEOUT)) {
 		dev_kfree_skb_any(adapter->ptp_tx_skb);
 		adapter->ptp_tx_skb = NULL;
+		clear_bit_unlock(__IGB_PTP_TX_IN_PROGRESS, &adapter->state);
 		adapter->tx_hwtstamp_timeouts++;
 		dev_warn(&adapter->pdev->dev, "clearing Tx timestamp hang");
 		return;
@@ -480,6 +481,7 @@ static void igb_ptp_tx_hwtstamp(struct igb_adapter *adapter)
 	skb_tstamp_tx(adapter->ptp_tx_skb, &shhwtstamps);
 	dev_kfree_skb_any(adapter->ptp_tx_skb);
 	adapter->ptp_tx_skb = NULL;
+	clear_bit_unlock(__IGB_PTP_TX_IN_PROGRESS, &adapter->state);
 }
 
 /**
@@ -857,6 +859,7 @@ void igb_ptp_stop(struct igb_adapter *adapter)
 	if (adapter->ptp_tx_skb) {
 		dev_kfree_skb_any(adapter->ptp_tx_skb);
 		adapter->ptp_tx_skb = NULL;
+		clear_bit_unlock(__IGB_PTP_TX_IN_PROGRESS, &adapter->state);
 	}
 
 	if (adapter->ptp_clock) {