Re: [PATCH v4 1/2] tiocsti-restrict : Add owner user namespace to tty_struct

[Alan Cox]

On Mon, 24 Apr 2017 01:15:11 -0400
Matt Brown <matt@xxxxxxxxx> wrote:

> This patch adds struct user_namespace *owner_user_ns to the tty_struct.
> Then it is set to current_user_ns() in the alloc_tty_struct function.
> 
> This is done to facilitate capability checks against the original user
> namespace that allocated the tty.
> 
> E.g. ns_capable(tty->owner_user_ns,CAP_SYS_ADMIN)
> 
> This combined with the use of user namespace's will allow hardening
> protections to be built to mitigate container escapes that utilize TTY
> ioctls such as TIOCSTI.

Regardles of the TIOCSTI usefulness this makes complete sense.

Alan