linux-kernel - Re: [kernel-hardening] Re: [PATCH v4 1/2] tiocsti-restrict : Add owner user namespace to tty

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Date:   Wed, 3 May 2017 23:42:06 -0500
From:   "Serge E. Hallyn" <serge@...lyn.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Matt Brown <matt@...tt.com>, Greg KH <gregkh@...uxfoundation.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        James Morris <jmorris@...ei.org>, Jiri Slaby <jslaby@...e.com>,
        Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jann Horn <jannh@...gle.com>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [kernel-hardening] Re: [PATCH v4 1/2] tiocsti-restrict : Add
 owner user namespace to tty_struct

On Wed, May 03, 2017 at 01:19:41PM -0700, Kees Cook wrote:
> On Wed, May 3, 2017 at 1:02 PM, Matt Brown <matt@...tt.com> wrote:
> > On 05/03/2017 03:45 PM, Greg KH wrote:
> >>
> >> On Wed, May 03, 2017 at 12:32:07PM -0700, Kees Cook wrote:
> >>>
> >>> On Mon, Apr 24, 2017 at 6:57 AM, Serge E. Hallyn <serge@...lyn.com>
> >>> wrote:
> >>>>
> >>>> Quoting Matt Brown (matt@...tt.com):
> >>>>>
> >>>>> 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.
> >>>>>
> >>>>> See: https://bugzilla.redhat.com/show_bug.cgi?id=1411256
> >>>>>
> >>>>> Signed-off-by: Matt Brown <matt@...tt.com>
> >>>>
> >>>>
> >>>> Acked-by: Serge Hallyn <serge@...lyn.com>
> >>>
> >>>
> >>> This Ack didn't end up in the v5, but I think it stands, yes?
> >>>
> >>> Greg, is the v5 okay to pull for you or would a v6 with Acks/Reviews
> >>> included be preferred?
> >>
> >>
> >> v6 would be great, and we are dropping patch 2 from the series, right?
> >> I was expecting this to be resent.  I'll start looking at new patches
> >> like this after 4.12-rc1 is out.
> >>
> >
> > I will create a v6 with the Acks/Reviews. I'd like to keep patch 2 in
> > since that got acked by at least Serge. (Kees also? or just patch 1?)
> 
> Sorry, I meant that patch 2's ack from serge got dropped accidentally.
> i.e. he Acked v4, but it wasn't in v5.
> 
> Serge, just to double-check, does your Ack stand?

Yes.

thanks,
-serge