netdev - Re: [PATCH v2 net-next 13/15] ipv6: anycast: Unify two error paths in ipv6_sock_ac

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Message-ID: <CANn89iJs9Z1PgRUTik63tLwTJATVMzZGe0Cpg1MNwCW0F2Mihg@mail.gmail.com>
Date: Thu, 26 Jun 2025 07:52:32 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Kuniyuki Iwashima <kuni1840@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Kuniyuki Iwashima <kuniyu@...gle.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next 13/15] ipv6: anycast: Unify two error paths in ipv6_sock_ac_join().

On Tue, Jun 24, 2025 at 1:26 PM Kuniyuki Iwashima <kuni1840@...il.com> wrote:
>
> From: Kuniyuki Iwashima <kuniyu@...gle.com>
>
> The next patch will replace __dev_get_by_index() and __dev_get_by_flags()
> to RCU + refcount version.
>
> Then, we will need to call dev_put() in some error paths.
>
> Let's unify two error paths to make the next patch cleaner.
>
> Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
> ---
>  net/ipv6/anycast.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/net/ipv6/anycast.c b/net/ipv6/anycast.c
> index 8440e7b27f6d..e0a1f9d7622c 100644
> --- a/net/ipv6/anycast.c
> +++ b/net/ipv6/anycast.c
> @@ -67,12 +67,11 @@ static u32 inet6_acaddr_hash(const struct net *net,
>  int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
>  {
>         struct ipv6_pinfo *np = inet6_sk(sk);
> +       struct ipv6_ac_socklist *pac = NULL;
> +       struct net *net = sock_net(sk);
>         struct net_device *dev = NULL;
>         struct inet6_dev *idev;
> -       struct ipv6_ac_socklist *pac;
> -       struct net *net = sock_net(sk);
> -       int     ishost = !net->ipv6.devconf_all->forwarding;
> -       int     err = 0;
> +       int err = 0, ishost;
>
>         ASSERT_RTNL();
>
> @@ -84,15 +83,22 @@ int ipv6_sock_ac_join(struct sock *sk, int ifindex, const struct in6_addr *addr)
>         if (ifindex)
>                 dev = __dev_get_by_index(net, ifindex);
>
> -       if (ipv6_chk_addr_and_flags(net, addr, dev, true, 0, IFA_F_TENTATIVE))
> -               return -EINVAL;
> +       if (ipv6_chk_addr_and_flags(net, addr, dev, true, 0, IFA_F_TENTATIVE)) {
> +               err = -EINVAL;
> +               goto error;
> +       }
>
>         pac = sock_kmalloc(sk, sizeof(struct ipv6_ac_socklist), GFP_KERNEL);
> -       if (!pac)
> -               return -ENOMEM;
> +       if (!pac) {
> +               err = -ENOMEM;
> +               goto error;
> +       }
> +
>         pac->acl_next = NULL;
>         pac->acl_addr = *addr;
>
> +       ishost = !net->ipv6.devconf_all->forwarding;

RTNL will no longer protect this read, you should add a READ_ONCE()

Other than that :

Reviewed-by: Eric Dumazet <edumazet@...gle.com>