linux-kernel - Re: [PATCH 3/7] net/tcp: Limit TCP_AO

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Date:   Tue, 21 Nov 2023 09:21:53 +0100
From:   Eric Dumazet <edumazet@...gle.com>
To:     Dmitry Safonov <dima@...sta.com>
Cc:     David Ahern <dsahern@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Francesco Ruggeri <fruggeri05@...il.com>,
        Salam Noureddine <noureddine@...sta.com>,
        Simon Horman <horms@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH 3/7] net/tcp: Limit TCP_AO_REPAIR to non-listen sockets

On Tue, Nov 21, 2023 at 3:01 AM Dmitry Safonov <dima@...sta.com> wrote:
>
> Listen socket is not an established TCP connection, so
> setsockopt(TCP_AO_REPAIR) doesn't have any impact.
>
> Restrict this uAPI for listen sockets.
>
> Fixes: faadfaba5e01 ("net/tcp: Add TCP_AO_REPAIR")
> Signed-off-by: Dmitry Safonov <dima@...sta.com>
> ---
>  net/ipv4/tcp.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 53bcc17c91e4..2836515ab3d7 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -3594,6 +3594,10 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
>                 break;
>
>         case TCP_AO_REPAIR:
> +               if (sk->sk_state == TCP_LISTEN) {
> +                       err = -ENOSTR;

ENOSTR is not used a single time in linux.

I suggest you use tcp_can_repair_sock() helper (and return -EPERM as
other TCP_REPAIR options)

> +                       break;
> +               }
>                 err = tcp_ao_set_repair(sk, optval, optlen);
>                 break;
>  #ifdef CONFIG_TCP_AO
> @@ -4293,6 +4297,8 @@ int do_tcp_getsockopt(struct sock *sk, int level,
>         }
>  #endif
>         case TCP_AO_REPAIR:
> +               if (sk->sk_state == TCP_LISTEN)
> +                       return -ENOSTR;
>                 return tcp_ao_get_repair(sk, optval, optlen);
>         case TCP_AO_GET_KEYS:
>         case TCP_AO_INFO: {
> --
> 2.42.0
>