linux-kernel - Re: [PATCH v2] efifb: prevent null-deref when iterating dmi

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Date:	Fri, 1 Nov 2013 13:09:20 +0100
From:	David Herrmann <dh.herrmann@...il.com>
To:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
Cc:	"linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
	James Bates <james.h.bates@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	James Bates <james.h.bates@...oo.com>
Subject: Re: [PATCH v2] efifb: prevent null-deref when iterating dmi_list

Hi

On Fri, Nov 1, 2013 at 12:10 PM, Jean-Christophe PLAGNIOL-VILLARD
<plagnioj@...osoft.com> wrote:
> On 17:17 Thu 31 Oct     , David Herrmann wrote:
>> Hi
>>
>> On Thu, Oct 31, 2013 at 11:45 AM, Jean-Christophe PLAGNIOL-VILLARD
>> <plagnioj@...osoft.com> wrote:
>> > On 18:40 Wed 02 Oct     , David Herrmann wrote:
>> >> The dmi_list array is initialized using gnu designated initializers, and
>> >> therefore may contain fewer explicitly defined entries as there are
>> >> elements in it. This is because the enum above with M_xyz constants
>> >> contains more items than the designated initializer. Those elements not
>> >> explicitly initialized are implicitly set to 0.
>> >>
>> >> Now efifb_setup() loops through all these array elements, and performs
>> >> a strcmp on each item. For non explicitly initialized elements this will
>> >> be a null pointer:
>> >>
>> >> This patch swaps the check order in the if statement, thus checks first
>> >> whether dmi_list[i].base is null.
>> >>
>> >> Signed-off-by: James Bates <james.h.bates@...oo.com>
>> >> Signed-off-by: David Herrmann <dh.herrmann@...il.com>
>> >
>> > with the simpleDRM arriving next merge I'm wondering if we need to keep it?
>>
>> SimpleDRM is not coming next merge-window. It's basically finished,
>> but I'm still working on the user-space side as its KMS api is highly
>> reduced compared to fully-featured DRM/KMS drivers. Maybe 3.13 will
>> work out.
>
> do you have a git tree for the simpleDRM that I can pull?

Sure, I usually push it to my fdo tree:
  http://cgit.freedesktop.org/~dvdhrm/linux/log/?h=simpledrm
But note that you shouldn't be using it right now. User-space fails on
it as SimpleDRM only provides a single KMS-FB. It also needs to be
adjusted to the new x86-sysfb changes and I am reworking the handover
to real drivers.

Cheers
David
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