linux-kernel - Re: [PATCH] drm/amd/powerplay: rv: Use designated initializers

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Date:   Fri, 28 Jul 2017 10:10:15 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Christian König <christian.koenig@....com>
Cc:     Alex Deucher <alexdeucher@...il.com>,
        David Airlie <airlied@...ux.ie>,
        LKML <linux-kernel@...r.kernel.org>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Alex Deucher <alexander.deucher@....com>,
        Rex Zhu <Rex.Zhu@....com>,
        Hawking Zhang <Hawking.Zhang@....com>
Subject: Re: [PATCH] drm/amd/powerplay: rv: Use designated initializers

On Fri, Jul 28, 2017 at 2:13 AM, Christian König
<christian.koenig@....com> wrote:
> Am 28.07.2017 um 03:43 schrieb Alex Deucher:
>>
>> On Tue, Jul 25, 2017 at 5:47 PM, Kees Cook <keescook@...omium.org> wrote:
>>>
>>> As done for vega10 in commit 3ddd396f6b57 ("drm/amd/powerplay: Use
>>> designated initializers") mark other tableFunction entries with
>>> designated
>>> initializers. The randstruct plugin requires designated initializers for
>>> structures that are entirely function pointers.
>>>
>>> Cc: Rex Zhu <Rex.Zhu@....com>
>>> Cc: Hawking Zhang <Hawking.Zhang@....com>
>>> Cc: Alex Deucher <alexander.deucher@....com>
>>> Signed-off-by: Kees Cook <keescook@...omium.org>
>>> ---
>>> If I can get an Ack for this, I'll carry it in the gcc-plugins tree,
>>> unless
>>> you think this is worth landing for v4.13, in which case, please take it
>>> now. :)
>>>
>> Acked-by: Alex Deucher <alexander.deucher@....com>
>>
>> I'm happy to take this through my tree if that is ok with you.
>
>
> I'm wondering a bit how the plugin detects that it can randomize a structure
> layout?
>
> We have a couple of structs where this would be fatal.

Automatic randomization only happen on struct that are entirely
function pointers.

See:
https://git.kernel.org/linus/313dd1b629219db50cad532dba6a3b3b22ffe622

And:
https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/commit/?id=914e2dfc61195a95868ae5c750690a7f1c87bc66

If you have any structures that are shared externally from the kernel,
I can mark them with __no_randomize_layout.

-Kees

-- 
Kees Cook
Pixel Security