netdev - [PATCH net-next 2/4] ipv6/sit: use DEV_STATS

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Message-ID: <20221115085358.2230729-3-edumazet@google.com>
Date:   Tue, 15 Nov 2022 08:53:56 +0000
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Eric Dumazet <edumazet@...gle.com>,
        syzbot <syzkaller@...glegroups.com>
Subject: [PATCH net-next 2/4] ipv6/sit: use DEV_STATS_INC() to avoid data-races

syzbot/KCSAN reported that multiple cpus are updating dev->stats.tx_error
concurrently.

This is because sit tunnels are NETIF_F_LLTX, meaning their ndo_start_xmit()
is not protected by a spinlock.

While original KCSAN report was about tx path, rx path has the same issue.

Reported-by: syzbot <syzkaller@...glegroups.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv6/sit.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 5703d3cbea9ba669c21d3f40bca347652077e6f0..70d81bba509390e29bd8c8ad1061ab81f92560dd 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -694,7 +694,7 @@ static int ipip6_rcv(struct sk_buff *skb)
 		skb->dev = tunnel->dev;
 
 		if (packet_is_spoofed(skb, iph, tunnel)) {
-			tunnel->dev->stats.rx_errors++;
+			DEV_STATS_INC(tunnel->dev, rx_errors);
 			goto out;
 		}
 
@@ -714,8 +714,8 @@ static int ipip6_rcv(struct sk_buff *skb)
 				net_info_ratelimited("non-ECT from %pI4 with TOS=%#x\n",
 						     &iph->saddr, iph->tos);
 			if (err > 1) {
-				++tunnel->dev->stats.rx_frame_errors;
-				++tunnel->dev->stats.rx_errors;
+				DEV_STATS_INC(tunnel->dev, rx_frame_errors);
+				DEV_STATS_INC(tunnel->dev, rx_errors);
 				goto out;
 			}
 		}
@@ -942,7 +942,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
 	if (!rt) {
 		rt = ip_route_output_flow(tunnel->net, &fl4, NULL);
 		if (IS_ERR(rt)) {
-			dev->stats.tx_carrier_errors++;
+			DEV_STATS_INC(dev, tx_carrier_errors);
 			goto tx_error_icmp;
 		}
 		dst_cache_set_ip4(&tunnel->dst_cache, &rt->dst, fl4.saddr);
@@ -950,14 +950,14 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
 
 	if (rt->rt_type != RTN_UNICAST && rt->rt_type != RTN_LOCAL) {
 		ip_rt_put(rt);
-		dev->stats.tx_carrier_errors++;
+		DEV_STATS_INC(dev, tx_carrier_errors);
 		goto tx_error_icmp;
 	}
 	tdev = rt->dst.dev;
 
 	if (tdev == dev) {
 		ip_rt_put(rt);
-		dev->stats.collisions++;
+		DEV_STATS_INC(dev, collisions);
 		goto tx_error;
 	}
 
@@ -970,7 +970,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
 		mtu = dst_mtu(&rt->dst) - t_hlen;
 
 		if (mtu < IPV4_MIN_MTU) {
-			dev->stats.collisions++;
+			DEV_STATS_INC(dev, collisions);
 			ip_rt_put(rt);
 			goto tx_error;
 		}
@@ -1009,7 +1009,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
 		struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom);
 		if (!new_skb) {
 			ip_rt_put(rt);
-			dev->stats.tx_dropped++;
+			DEV_STATS_INC(dev, tx_dropped);
 			kfree_skb(skb);
 			return NETDEV_TX_OK;
 		}
@@ -1039,7 +1039,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
 	dst_link_failure(skb);
 tx_error:
 	kfree_skb(skb);
-	dev->stats.tx_errors++;
+	DEV_STATS_INC(dev, tx_errors);
 	return NETDEV_TX_OK;
 }
 
@@ -1058,7 +1058,7 @@ static netdev_tx_t sit_tunnel_xmit__(struct sk_buff *skb,
 	return NETDEV_TX_OK;
 tx_error:
 	kfree_skb(skb);
-	dev->stats.tx_errors++;
+	DEV_STATS_INC(dev, tx_errors);
 	return NETDEV_TX_OK;
 }
 
@@ -1087,7 +1087,7 @@ static netdev_tx_t sit_tunnel_xmit(struct sk_buff *skb,
 	return NETDEV_TX_OK;
 
 tx_err:
-	dev->stats.tx_errors++;
+	DEV_STATS_INC(dev, tx_errors);
 	kfree_skb(skb);
 	return NETDEV_TX_OK;
 
-- 
2.38.1.431.g37b22c650d-goog