Re: [PATCH] net/ipv4: Replace tcp_ca_get_name_by_key()'s strncpy() with strscpy()

[Eric Dumazet]

On Thu, Jul 11, 2024 at 10:16 AM Kees Cook <kees@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: David Ahern <dsahern@xxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> ---
>  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.