linux-kernel - Re: [PATCH net-next] ipv6: annotate data-races around devconf->rpl_seg

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Message-ID: <CAAVpQUDA5gCi--n9N7PQZC3rDBxhZxMW8AUFoaGs+09oT6Vebg@mail.gmail.com>
Date: Mon, 25 Aug 2025 20:17:03 -0700
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: Yue Haibing <yuehaibing@...wei.com>
Cc: davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, horms@...nel.org, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] ipv6: annotate data-races around devconf->rpl_seg_enabled

On Mon, Aug 25, 2025 at 7:51 PM Yue Haibing <yuehaibing@...wei.com> wrote:
>
> devconf->rpl_seg_enabled can be changed concurrently from
> /proc/sys/net/ipv6/conf, annotate lockless reads on it.
>
> Signed-off-by: Yue Haibing <yuehaibing@...wei.com>
> ---
>  net/ipv6/exthdrs.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
> index d1ef9644f826..a23eb8734e15 100644
> --- a/net/ipv6/exthdrs.c
> +++ b/net/ipv6/exthdrs.c
> @@ -494,10 +494,8 @@ static int ipv6_rpl_srh_rcv(struct sk_buff *skb)
>
>         idev = __in6_dev_get(skb->dev);
>
> -       accept_rpl_seg = net->ipv6.devconf_all->rpl_seg_enabled;
> -       if (accept_rpl_seg > idev->cnf.rpl_seg_enabled)
> -               accept_rpl_seg = idev->cnf.rpl_seg_enabled;
> -
> +       accept_rpl_seg = min(READ_ONCE(net->ipv6.devconf_all->rpl_seg_enabled),
> +                            READ_ONCE(idev->cnf.rpl_seg_enabled));
>         if (!accept_rpl_seg) {

Orthogonal to this change, but rpl_seg_enabled is missing .extra1/2
or this condition should be adjusted like other knobs that recognises
 <0 as disabled, .e.g. keep_addr_on_down, etc.


>                 kfree_skb(skb);
>                 return -1;
> --
> 2.34.1
>