netdev - Re: [PATCH] tcp: md5: incorrect tcp_header

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Date:   Wed, 20 Apr 2022 17:20:35 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Francesco Ruggeri <fruggeri@...sta.com>
Cc:     Paolo Abeni <pabeni@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
        David Ahern <dsahern@...nel.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Miller <davem@...emloft.net>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] tcp: md5: incorrect tcp_header_len for incoming connections

On Wed, Apr 20, 2022 at 4:57 PM Francesco Ruggeri <fruggeri@...sta.com> wrote:
>
> In tcp_create_openreq_child we adjust tcp_header_len for md5 using the
> remote address in newsk. But that address is still 0 in newsk at this
> point, and it is only set later by the callers (tcp_v[46]_syn_recv_sock).
> Use the address from the request socket instead.
>

Nice catch.

This seems like a day-0 bug, right ?

Do you agree on adding

Fixes: cfb6eeb4c860 ("[TCP]: MD5 Signature Option (RFC2385) support.")

Thanks.

> Signed-off-by: Francesco Ruggeri <fruggeri@...sta.com>
> ---
>  net/ipv4/tcp_minisocks.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
> index 6366df7aaf2a..6854bb1fb32b 100644
> --- a/net/ipv4/tcp_minisocks.c
> +++ b/net/ipv4/tcp_minisocks.c
> @@ -531,7 +531,7 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
>         newtp->tsoffset = treq->ts_off;
>  #ifdef CONFIG_TCP_MD5SIG
>         newtp->md5sig_info = NULL;      /*XXX*/
> -       if (newtp->af_specific->md5_lookup(sk, newsk))
> +       if (treq->af_specific->req_md5_lookup(sk, req_to_sk(req)))
>                 newtp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
>  #endif
>         if (skb->len >= TCP_MSS_DEFAULT + newtp->tcp_header_len)
> --
> 2.28.0
>
>