linux-kernel - Re: [kernel-hardening] Re: [RFC v1] mm: SLAB freelist randomization

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Message-ID: <CAJcbSZFx4rT6fXKvOF-wgHTSZBgqfQGw0qn=JqwAygNHDVUvNQ@mail.gmail.com>
Date:	Thu, 7 Apr 2016 09:35:46 -0700
From:	Thomas Garnier <thgarnie@...gle.com>
To:	Yves-Alexis Perez <corsac@...ian.org>
Cc:	kernel-hardening@...ts.openwall.com,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Thelen <gthelen@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>,
	Laura Abbott <labbott@...oraproject.org>
Subject: Re: [kernel-hardening] Re: [RFC v1] mm: SLAB freelist randomization

That's a use after free. The randomization of the freelist should not
have much effect on that. I was going to quote this exploit that is
applicable to SLAB as well:
https://jon.oberheide.org/blog/2010/09/10/linux-kernel-can-slub-overflow

Regards.
Thomas

On Thu, Apr 7, 2016 at 9:17 AM, Yves-Alexis Perez <corsac@...ian.org> wrote:
> On mer., 2016-04-06 at 14:45 -0700, Kees Cook wrote:
>> > This security feature reduces the predictability of
>> > the kernel slab allocator against heap overflows.
>>
>> I would add "... rendering attacks much less stable." And if you can
>> find a specific example exploit that is foiled by this, I would refer
>> to it.
>
> One good example might (or might not) be the keyring issue from earlier this
> year (CVE-2016-0728):
>
> http://perception-point.io/2016/01/14/analysis-and-exploitation-of-a-linux-ker
> nel-vulnerability-cve-2016-0728/
>
> Regards,
> --
> Yves-Alexis
>