linux-kernel - Re: + syscalls-x86-add-__nr_kcmp-syscall-v8.patch added to -mm tree

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Date:	Tue, 10 Apr 2012 20:02:21 -0400
From:	Valdis.Kletnieks@...edu
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Andrey Vagin <avagin@...nvz.org>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Glauber Costa <glommer@...allels.com>,
	Andi Kleen <andi@...stfloor.org>, Tejun Heo <tj@...nel.org>,
	Matt Helsley <matthltc@...ibm.com>,
	Pekka Enberg <penberg@...nel.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Vasiliy Kulikov <segoon@...nwall.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Michal Marek <mmarek@...e.cz>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>
Subject: Re: + syscalls-x86-add-__nr_kcmp-syscall-v8.patch added to -mm tree

On Mon, 09 Apr 2012 16:22:38 -0700, "H. Peter Anvin" said:
> On 04/09/2012 03:24 PM, Cyrill Gorcunov wrote:
> >>
> >> Having re-read most of the (enormous) email discussion on the kcmp()
> >> syscall patch, I'm thinking:
> >>
> >> - Nobody seems to understand the obfuscation logic.  Jon sounded
> >>   confused, Oleg sounds confused and it's rather unclear what it does,
> >>   how it does it and why it does it.
> >
> > The obfuscation logic was done with great help from hpa@. And the main
> > idea was to have ordered results after obfuscation. Per-type noise increase
> > randomization of results. So Andrew, I actually dont know what to add
> > here. We don't want to provide kernel order back to user-space in
> > naked manner.
> >
>
> The obfuscation logic is to provide a 1:1 mapping but which doesn't
> preserve ordering, thereby avoid leaking information of kernel pointers
> to user space.

Oh, OK... Ignore my previous note then.  But we should lose the comment
that implies we have an ordering?

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