Re: [PATCH net-next] scm: fix MSG_CTRUNC setting condition for SO_PASSSEC

[Leon Romanovsky <leon@kernel.org>]

On Sun, Feb 26, 2023 at 09:17:30PM +0100, Alexander Mikhalitsyn wrote:
> Currently, we set MSG_CTRUNC flag is we have no
> msg_control buffer provided and SO_PASSCRED is set
> or if we have pending SCM_RIGHTS.
> 
> For some reason we have no corresponding check for
> SO_PASSSEC.
> 
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
> ---
>  include/net/scm.h | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)

Is it a bugfix? If yes, it needs Fixes line.

> 
> diff --git a/include/net/scm.h b/include/net/scm.h
> index 1ce365f4c256..585adc1346bd 100644
> --- a/include/net/scm.h
> +++ b/include/net/scm.h
> @@ -105,16 +105,27 @@ static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct sc
>  		}
>  	}
>  }
> +
> +static inline bool scm_has_secdata(struct socket *sock)
> +{
> +	return test_bit(SOCK_PASSSEC, &sock->flags);
> +}
>  #else
>  static inline void scm_passec(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm)
>  { }
> +
> +static inline bool scm_has_secdata(struct socket *sock)
> +{
> +	return false;
> +}
>  #endif /* CONFIG_SECURITY_NETWORK */

There is no need in this ifdef, just test bit directly.

>  
>  static __inline__ void scm_recv(struct socket *sock, struct msghdr *msg,
>  				struct scm_cookie *scm, int flags)
>  {
>  	if (!msg->msg_control) {
> -		if (test_bit(SOCK_PASSCRED, &sock->flags) || scm->fp)
> +		if (test_bit(SOCK_PASSCRED, &sock->flags) || scm->fp ||
> +		    scm_has_secdata(sock))
>  			msg->msg_flags |= MSG_CTRUNC;
>  		scm_destroy(scm);
>  		return;
> -- 
> 2.34.1
>