linux-kernel - Re: [Intel-gfx] [PATCH] drm/i915: Sanity check incoming ioctl data for a NULL pointer

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Message-ID: <CAPM=9txw7pPT195p1nJrr5=TvTBGsd6G+a7N5C+fxQgP0Eof3w@mail.gmail.com>
Date:	Mon, 18 Mar 2013 07:42:58 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Chris Wilson <chris@...is-wilson.co.uk>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	Ben Widawsky <ben@...dawsk.net>,
	Tommi Rantala <tt.rantala@...il.com>,
	David Airlie <airlied@...ux.ie>,
	intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, Dave Jones <davej@...hat.com>
Subject: Re: [Intel-gfx] [PATCH] drm/i915: Sanity check incoming ioctl data
 for a NULL pointer

On Mon, Mar 18, 2013 at 7:40 AM, Chris Wilson <chris@...is-wilson.co.uk> wrote:
> On Sun, Mar 17, 2013 at 08:50:03PM +0100, Daniel Vetter wrote:
>> On Sat, Mar 16, 2013 at 11:19 AM, Chris Wilson <chris@...is-wilson.co.uk> wrote:
>> > If *userspace* doesn't request either IOC_IN | IOC_OUT in their ioctl
>> > command (which are seperate from the ioctl number), then kdata is set to
>> > NULL.
>>
>> Doesn't that mean that we need these checks everywhere? Or at least a
>> fixup in drm core proper?
>
> That's my conclusion. We either add a flag to ask drm_ioctl to prevent
> passing NULL pointers (as the existing behaviour may be useful
> somewhere, and I have not checked all callees) or saturate our callbacks
> with NULL checks.

Do we have the kernel's expected IOC_IN/IOC_OUT flags at that point as well?

we could check them and block NULL in that case.

Dave.
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