Re: [PATCH net-next 4/9] sit: annotate data-races around tunnel->fwmark

[Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>]

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> ipip6_tunnel_xmit() runs locklessly (dev->lltx == true) and reads
> tunnel->fwmark.
> 
> In preparation for converting ipip6_fill_info() to run without RTNL,
> add READ_ONCE() and WRITE_ONCE() annotations around tunnel->fwmark.

Acked-by: Lorenzo Bianconi <lorenzo.bianconi@oss.qualcomm.com>

> 
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
>  net/ipv6/sit.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
> index 9a2bbd76d3794849cd11c6530ba1303bf53fa388..e85fa80e80d1ad2c593b860685b9f5bac21e66d9 100644
> --- a/net/ipv6/sit.c
> +++ b/net/ipv6/sit.c
> @@ -929,7 +929,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
>  	if (!dst && !ipip6_tunnel_dst_find(skb, &dst, false))
>  		goto tx_error;
>  
> -	flowi4_init_output(&fl4, tunnel->parms.link, tunnel->fwmark,
> +	flowi4_init_output(&fl4, tunnel->parms.link, READ_ONCE(tunnel->fwmark),
>  			   tos & INET_DSCP_MASK, RT_SCOPE_UNIVERSE,
>  			   IPPROTO_IPV6, 0, dst, tiph->saddr, 0, 0,
>  			   sock_net_uid(tunnel->net, NULL));
> @@ -1153,7 +1153,7 @@ static void ipip6_tunnel_update(struct ip_tunnel *t,
>  	t->parms.iph.frag_off = p->iph.frag_off;
>  	if (t->parms.link != p->link || t->fwmark != fwmark) {
>  		t->parms.link = p->link;
> -		t->fwmark = fwmark;
> +		WRITE_ONCE(t->fwmark, fwmark);
>  		ipip6_tunnel_bind_dev(t->dev);
>  	}
>  	dst_cache_reset(&t->dst_cache);
> @@ -1706,7 +1706,7 @@ static int ipip6_fill_info(struct sk_buff *skb, const struct net_device *dev)
>  	    nla_put_u8(skb, IFLA_IPTUN_PROTO, parm->iph.protocol) ||
>  	    nla_put_be16(skb, IFLA_IPTUN_FLAGS,
>  			 ip_tunnel_flags_to_be16(parm->i_flags)) ||
> -	    nla_put_u32(skb, IFLA_IPTUN_FWMARK, tunnel->fwmark))
> +	    nla_put_u32(skb, IFLA_IPTUN_FWMARK, READ_ONCE(tunnel->fwmark)))
>  		goto nla_put_failure;
>  
>  #ifdef CONFIG_IPV6_SIT_6RD
> -- 
> 2.55.0.979.g7e5102b832-goog
> 

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