linux-kernel - Re: [PATCH RFC 3/4] x86/pti: don't mark the user PGD with _PAGE

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Message-ID: <20180108183515.7ougslrseroramrs@gmail.com>
Date:   Mon, 8 Jan 2018 19:35:15 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Alan Cox <gnomes@...rguk.ukuu.org.uk>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>, Willy Tarreau <w@....eu>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        torvalds@...ux-foundation.org
Subject: Re: [PATCH RFC 3/4] x86/pti: don't mark the user PGD with _PAGE_NX.


* Alan Cox <gnomes@...rguk.ukuu.org.uk> wrote:

> > The simplest model is indeed child inheritance tree propagation - plus perhaps the 
> > ability for a thread to change its *own* PTI status, which obviously doesn't 
> > create any deep "process lookup" or cross-CPU complications.
> > 
> > ( Note that here I only mean "simple to implement" - we might decide to not offer
> >   the ABI. )
> 
> I still think cgroups are the best model for this. In particular it
> naturally fits things like containers, or network facing apps that fork
> helpers.

I think the suggested exec() time inheritance model would naturally also cover 
cgroups (without tying the ABI to cgroups) - as containers typically get inherited 
from a single binary. A bit like how various personality bits get propagated.

Thanks,

	Ingo