[PATCH] linux: handle MPTCP consistently with TCP

[Casey Schaufler]

On 12/16/2020 3:55 AM, Paolo Abeni wrote:
> The MPTCP protocol uses a specific protocol value, even if
> it's an extension to TCP. Additionally, MPTCP sockets
> could 'fall-back' to TCP at run-time, depending on peer MPTCP
> support and available resources.
>
> As a consequence of the specific protocol number, selinux
> applies the raw_socket class to MPTCP sockets.

Have you looked at the implications for Smack?

>
> Existing TCP application converted to MPTCP - or forced to
> use MPTCP socket with user-space hacks - will need an
> updated policy to run successfully.
>
> This change lets selinux attach the TCP socket class to
> MPTCP sockets, too, so that no policy changes are needed in
> the above scenario.
>
> Note that the MPTCP is setting, propagating and updating the
> security context on all the subflows and related request
> socket.
>
> Link: https://lore.kernel.org/linux-security-module/CAHC9VhTaK3xx0hEGByD2zxfF7fadyPP1kb-WeWH_YCyq9X-sRg@mail.gmail.com/T/#t
> Signed-off-by: Paolo Abeni <pabeni at redhat.com>
> ---
>  security/selinux/hooks.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 6fa593006802..451bded67d9c 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -1120,7 +1120,8 @@ static inline u16 inode_mode_to_security_class(umode_t mode)
>  
>  static inline int default_protocol_stream(int protocol)
>  {
> -	return (protocol == IPPROTO_IP || protocol == IPPROTO_TCP);
> +	return (protocol == IPPROTO_IP || protocol == IPPROTO_TCP ||
> +		protocol == IPPROTO_MPTCP);
>  }
>  
>  static inline int default_protocol_dgram(int protocol)