[RFC PATCH v2 1/8] landlock: Fix non-TCP sockets restriction

[Mickaël Salaün]

On Thu, Oct 17, 2024 at 07:04:47PM +0800, Mikhail Ivanov wrote:
> Do not check TCP access right if socket protocol is not IPPROTO_TCP.
> LANDLOCK_ACCESS_NET_BIND_TCP and LANDLOCK_ACCESS_NET_CONNECT_TCP
> should not restrict bind(2) and connect(2) for non-TCP protocols
> (SCTP, MPTCP, SMC).
> 
> sk_is_tcp() is used for this to check address family of the socket
> before doing INET-specific address length validation. This is required
> for error consistency.
> 
> Closes: https://github.com/landlock-lsm/linux/issues/40
> Fixes: fff69fb03dde ("landlock: Support network rules with TCP bind and connect")
> Signed-off-by: Mikhail Ivanov <ivanov.mikhail1 at huawei-partners.com>
> ---
> 
> Changes since v1:
> * Validate socket family (=INET{,6}) before any other checks
>   with sk_is_tcp().
> ---
>  security/landlock/net.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/security/landlock/net.c b/security/landlock/net.c
> index fdc1bb0a9c5d..1e80782ba239 100644
> --- a/security/landlock/net.c
> +++ b/security/landlock/net.c
> @@ -66,8 +66,8 @@ static int current_check_access_socket(struct socket *const sock,
>  	if (WARN_ON_ONCE(dom->num_layers < 1))
>  		return -EACCES;
>  
> -	/* Checks if it's a (potential) TCP socket. */
> -	if (sock->type != SOCK_STREAM)
> +	/* Do not restrict non-TCP sockets. */

You can remove this comment because the following check is explicit.

> +	if (!sk_is_tcp(sock->sk))
>  		return 0;
>  
>  	/* Checks for minimal header length to safely read sa_family. */
> -- 
> 2.34.1
> 
>