linux-kernel - Re: [PATCH 26/26] x86, pkeys: Documentation

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Message-ID: <CAGXu5j+j92EPEwv9O4cX92zJDTyBEz3WtQ2CDHT0KmqJ6bCmGQ@mail.gmail.com>
Date:	Thu, 1 Oct 2015 13:39:07 -0700
From:	Kees Cook <keescook@...gle.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Dave Hansen <dave@...1.net>, "x86@...nel.org" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH 26/26] x86, pkeys: Documentation

On Thu, Oct 1, 2015 at 4:17 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
> * Dave Hansen <dave@...1.net> wrote:
>
>> > If yes then this could be a significant security feature / usecase for pkeys:

Which CPUs (will) have pkeys?

>> > executable sections of shared libraries and binaries could be mapped with pkey
>> > access disabled. If I read the Intel documentation correctly then that should
>> > be possible.
>>
>> Agreed.  I've even heard from some researchers who are interested in this:
>>
>> https://www.infsec.cs.uni-saarland.de/wp-content/uploads/sites/2/2014/10/nuernberger2014ccs_disclosure.pdf
>
> So could we try to add an (opt-in) kernel option that enables this transparently
> and automatically for all PROT_EXEC && !PROT_WRITE mappings, without any
> user-space changes and syscalls necessary?

I would like this very much. :)

> Beyond the security improvement, this would enable this hardware feature on most
> x86 Linux distros automatically, on supported hardware, which is good for testing.
>
> Assuming it boots up fine on a typical distro, i.e. assuming that there are no
> surprises where PROT_READ && PROT_EXEC sections are accessed as data.

I can't wait to find out what implicitly expects PROT_READ from
PROT_EXEC mappings. :)

-Kees

-- 
Kees Cook
Chrome OS Security
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