macsec: use DEV_STATS_INC()

syzbot/KCSAN reported data-races in macsec whenever dev->stats fields
are updated.

It appears all of these updates can happen from multiple cpus.

Adopt SMP safe DEV_STATS_INC() to update dev->stats fields.

Fixes: c09440f ("macsec: introduce IEEE 802.1AE driver")
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: edumazet

drivers/net/macsec.c

@@ -743,7 +743,7 @@ static bool macsec_post_decrypt(struct sk_buff *skb, struct macsec_secy *secy, u
 		u64_stats_update_begin(&rxsc_stats->syncp);
 		rxsc_stats->stats.InPktsLate++;
 		u64_stats_update_end(&rxsc_stats->syncp);
-		secy->netdev->stats.rx_dropped++;
+		DEV_STATS_INC(secy->netdev, rx_dropped);
 		return false;
 	}
 
@@ -767,7 +767,7 @@ static bool macsec_post_decrypt(struct sk_buff *skb, struct macsec_secy *secy, u
 			rxsc_stats->stats.InPktsNotValid++;
 			u64_stats_update_end(&rxsc_stats->syncp);
 			this_cpu_inc(rx_sa->stats->InPktsNotValid);
-			secy->netdev->stats.rx_errors++;
+			DEV_STATS_INC(secy->netdev, rx_errors);
 			return false;
 		}
 
@@ -1069,7 +1069,7 @@ static enum rx_handler_result handle_not_macsec(struct sk_buff *skb)
 			u64_stats_update_begin(&secy_stats->syncp);
 			secy_stats->stats.InPktsNoTag++;
 			u64_stats_update_end(&secy_stats->syncp);
-			macsec->secy.netdev->stats.rx_dropped++;
+			DEV_STATS_INC(macsec->secy.netdev, rx_dropped);
 			continue;
 		}
 
@@ -1179,7 +1179,7 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
 		u64_stats_update_begin(&secy_stats->syncp);
 		secy_stats->stats.InPktsBadTag++;
 		u64_stats_update_end(&secy_stats->syncp);
-		secy->netdev->stats.rx_errors++;
+		DEV_STATS_INC(secy->netdev, rx_errors);
 		goto drop_nosa;
 	}
 
@@ -1196,7 +1196,7 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
 			u64_stats_update_begin(&rxsc_stats->syncp);
 			rxsc_stats->stats.InPktsNotUsingSA++;
 			u64_stats_update_end(&rxsc_stats->syncp);
-			secy->netdev->stats.rx_errors++;
+			DEV_STATS_INC(secy->netdev, rx_errors);
 			if (active_rx_sa)
 				this_cpu_inc(active_rx_sa->stats->InPktsNotUsingSA);
 			goto drop_nosa;
@@ -1230,7 +1230,7 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
 			u64_stats_update_begin(&rxsc_stats->syncp);
 			rxsc_stats->stats.InPktsLate++;
 			u64_stats_update_end(&rxsc_stats->syncp);
-			macsec->secy.netdev->stats.rx_dropped++;
+			DEV_STATS_INC(macsec->secy.netdev, rx_dropped);
 			goto drop;
 		}
 	}
@@ -1271,7 +1271,7 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
 	if (ret == NET_RX_SUCCESS)
 		count_rx(dev, len);
 	else
-		macsec->secy.netdev->stats.rx_dropped++;
+		DEV_STATS_INC(macsec->secy.netdev, rx_dropped);
 
 	rcu_read_unlock();
 
@@ -1308,7 +1308,7 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
 			u64_stats_update_begin(&secy_stats->syncp);
 			secy_stats->stats.InPktsNoSCI++;
 			u64_stats_update_end(&secy_stats->syncp);
-			macsec->secy.netdev->stats.rx_errors++;
+			DEV_STATS_INC(macsec->secy.netdev, rx_errors);
 			continue;
 		}
 
@@ -1327,7 +1327,7 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
 			secy_stats->stats.InPktsUnknownSCI++;
 			u64_stats_update_end(&secy_stats->syncp);
 		} else {
-			macsec->secy.netdev->stats.rx_dropped++;
+			DEV_STATS_INC(macsec->secy.netdev, rx_dropped);
 		}
 	}
 
@@ -3422,15 +3422,15 @@ static netdev_tx_t macsec_start_xmit(struct sk_buff *skb,
 
 	if (!secy->operational) {
 		kfree_skb(skb);
-		dev->stats.tx_dropped++;
+		DEV_STATS_INC(dev, tx_dropped);
 		return NETDEV_TX_OK;
 	}
 
 	len = skb->len;
 	skb = macsec_encrypt(skb, dev);
 	if (IS_ERR(skb)) {
 		if (PTR_ERR(skb) != -EINPROGRESS)
-			dev->stats.tx_dropped++;
+			DEV_STATS_INC(dev, tx_dropped);
 		return NETDEV_TX_OK;
 	}
 
@@ -3667,9 +3667,9 @@ static void macsec_get_stats64(struct net_device *dev,
 
 	dev_fetch_sw_netstats(s, dev->tstats);
 
-	s->rx_dropped = dev->stats.rx_dropped;
-	s->tx_dropped = dev->stats.tx_dropped;
-	s->rx_errors = dev->stats.rx_errors;
+	s->rx_dropped = atomic_long_read(&dev->stats.__rx_dropped);
+	s->tx_dropped = atomic_long_read(&dev->stats.__tx_dropped);
+	s->rx_errors = atomic_long_read(&dev->stats.__rx_errors);
 }
 
 static int macsec_get_iflink(const struct net_device *dev)