linux-kernel - Re: [PATCH] drm/i915: bounds check execbuffer relocations

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Message-ID: <CAGXu5jKJqkWoiQOwWrfy33KDoSZdH_GB6O5=pr+yxi7U74pg8Q@mail.gmail.com>
Date:	Mon, 11 Mar 2013 14:08:22 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Chris Wilson <chris@...is-wilson.co.uk>,
	Kees Cook <keescook@...omium.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH] drm/i915: bounds check execbuffer relocations

On Mon, Mar 11, 2013 at 1:52 PM, Chris Wilson <chris@...is-wilson.co.uk> wrote:
> On Mon, Mar 11, 2013 at 12:27:16PM -0700, Kees Cook wrote:
>> It is possible to wrap the counter used to allocate the buffer for
>> relocation copies. This could lead to heap writing overflows.
>
> Seems a sensible check, just in the wrong location. You need to do the
> checking upfront in validate_exec_list() so that the error condition is
> always hit and that the limits are applied consistently to all
> execbuffers.

I opted for it here because it kept it out of the fast path which
didn't need this check (it uses a list rather than an array). I will
move it to validate_exec_list().

Thanks!

-Kees

--
Kees Cook
Chrome OS Security
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