linux-kernel - Re: [PATCH] net/ipv4: Replace tcp_ca_get_name_by

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Message-ID: <CANn89iKqZD68w1QtM3ztL_X290tj_EGyWRvFrhyAz-=T+GkogQ@mail.gmail.com>
Date: Thu, 11 Jul 2024 10:38:01 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Kees Cook <kees@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] net/ipv4: Replace tcp_ca_get_name_by_key()'s strncpy()
 with strscpy()

On Thu, Jul 11, 2024 at 10:16 AM Kees Cook <kees@...nel.org> wrote:
>
> Replace the deprecated[1] use of strncpy() in tcp_ca_get_name_by_key().
> The only caller passes the results to nla_put_string(), so trailing
> padding is not needed.
>
> Since passing "buffer" decays it to a pointer, the size can't be
> trivially determined by the compiler. ca->name is the same length,
> so strscpy() won't fail (when ca->name is NUL-terminated). Include the
> length explicitly instead of using the 2-argument strscpy().
>
> Link: https://github.com/KSPP/linux/issues/90 [1]
> Signed-off-by: Kees Cook <kees@...nel.org>
> ---
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: David Ahern <dsahern@...nel.org>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: netdev@...r.kernel.org
> ---
>  net/ipv4/tcp_cong.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c
> index 28ffcfbeef14..2a303a7cba59 100644
> --- a/net/ipv4/tcp_cong.c
> +++ b/net/ipv4/tcp_cong.c
> @@ -203,9 +203,10 @@ char *tcp_ca_get_name_by_key(u32 key, char *buffer)
>
>         rcu_read_lock();
>         ca = tcp_ca_find_key(key);
> -       if (ca)
> -               ret = strncpy(buffer, ca->name,
> -                             TCP_CA_NAME_MAX);
> +       if (ca) {
> +               strscpy(buffer, ca->name, TCP_CA_NAME_MAX);
> +               ret = buffer;
> +       }
>         rcu_read_unlock();
>

Ok, but what about tcp_get_default_congestion_control() ?

Thanks.