netdev - Re: [PATCH net] wireguard: use DEV_STATS

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Date: Fri, 17 Nov 2023 09:34:47 +0800
From: Hangbin Liu <liuhangbin@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, eric.dumazet@...il.com,
	syzbot <syzkaller@...glegroups.com>,
	"Jason A . Donenfeld" <Jason@...c4.com>
Subject: Re: [PATCH net] wireguard: use DEV_STATS_INC()

On Thu, Nov 16, 2023 at 10:02:17AM +0000, Eric Dumazet wrote:
> wg_xmit() can be called concurrently, KCSAN reported [1]
> some device stats updates can be lost.
> 
> Use DEV_STATS_INC() for this unlikely case.
> 
> [1]
> BUG: KCSAN: data-race in wg_xmit / wg_xmit
> 
> read-write to 0xffff888104239160 of 8 bytes by task 1375 on cpu 0:
> wg_xmit+0x60f/0x680 drivers/net/wireguard/device.c:231
> __netdev_start_xmit include/linux/netdevice.h:4918 [inline]
> netdev_start_xmit include/linux/netdevice.h:4932 [inline]
> xmit_one net/core/dev.c:3543 [inline]
> dev_hard_start_xmit+0x11b/0x3f0 net/core/dev.c:3559
> ...
> 
> read-write to 0xffff888104239160 of 8 bytes by task 1378 on cpu 1:
> wg_xmit+0x60f/0x680 drivers/net/wireguard/device.c:231
> __netdev_start_xmit include/linux/netdevice.h:4918 [inline]
> netdev_start_xmit include/linux/netdevice.h:4932 [inline]
> xmit_one net/core/dev.c:3543 [inline]
> dev_hard_start_xmit+0x11b/0x3f0 net/core/dev.c:3559
> ...
> 
> Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Jason A. Donenfeld <Jason@...c4.com>
> ---
>  drivers/net/wireguard/device.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireguard/device.c b/drivers/net/wireguard/device.c
> index 258dcc1039216f311a223fd348295d4b5e03a3ed..deb9636b0ecf8f47e832a0b07e9e049ba19bdf16 100644
> --- a/drivers/net/wireguard/device.c
> +++ b/drivers/net/wireguard/device.c
> @@ -210,7 +210,7 @@ static netdev_tx_t wg_xmit(struct sk_buff *skb, struct net_device *dev)
>  	 */
>  	while (skb_queue_len(&peer->staged_packet_queue) > MAX_STAGED_PACKETS) {
>  		dev_kfree_skb(__skb_dequeue(&peer->staged_packet_queue));
> -		++dev->stats.tx_dropped;
> +		DEV_STATS_INC(dev, tx_dropped);
>  	}
>  	skb_queue_splice_tail(&packets, &peer->staged_packet_queue);
>  	spin_unlock_bh(&peer->staged_packet_queue.lock);
> @@ -228,7 +228,7 @@ static netdev_tx_t wg_xmit(struct sk_buff *skb, struct net_device *dev)
>  	else if (skb->protocol == htons(ETH_P_IPV6))
>  		icmpv6_ndo_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_ADDR_UNREACH, 0);
>  err:
> -	++dev->stats.tx_errors;
> +	DEV_STATS_INC(dev, tx_errors);
>  	kfree_skb(skb);
>  	return ret;
>  }
> -- 
> 2.43.0.rc0.421.g78406f8d94-goog
> 

Reviewed-by: Hangbin Liu <liuhangbin@...il.com>

BTW, what about the receive part function wg_packet_consume_data_done(), do
we need to use DEV_STATS_INC()?

Thanks
Hangbin