linux-kernel - Re: [PATCH] drm/amdgpu: Fix NULL pointer dereference

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Message-ID: <436116c9-6ce4-87cc-b1cd-f44b72fcfb35@amd.com>
Date:   Fri, 8 Apr 2022 16:30:06 +0200
From:   Christian König <christian.koenig@....com>
To:     Grigory Vasilyev <h0tc0d3@...il.com>,
        Simon Ser <contact@...rsion.fr>
Cc:     Bas Nieuwenhuizen <bas@...nieuwenhuizen.nl>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Melissa Wen <mwen@...lia.com>,
        Alex Deucher <alexander.deucher@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Michel Dänzer <mdaenzer@...hat.com>,
        Evan Quan <evan.quan@....com>,
        Sean Paul <seanpaul@...omium.org>,
        Qingqing Zhuo <qingqing.zhuo@....com>,
        amd-gfx mailing list <amd-gfx@...ts.freedesktop.org>,
        ML dri-devel <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/amdgpu: Fix NULL pointer dereference

Am 08.04.22 um 15:21 schrieb Grigory Vasilyev:
> Simon Ser and Bas Nieuwenhuizen, do you understand that you are
> proposing to make the code less safe in the future? In the future,
> someone might rewrite the code and we'll get an error.

Which is perfectly fine.

See error handling is to handle userspace or hardware errors and *not* 
coding errors.

Testing all pointers for NULL without any reason is not defensive, but 
rather the exactly opposite since it helps hiding real bugs.

Regards,
Christian.

>
> пт, 8 апр. 2022 г. в 14:48, Simon Ser <contact@...rsion.fr>:
>> On Friday, April 8th, 2022 at 13:28, Bas Nieuwenhuizen <bas@...nieuwenhuizen.nl> wrote:
>>
>>> On Fri, Apr 8, 2022 at 12:01 PM Simon Ser contact@...rsion.fr wrote:
>>>
>>>> Is amdgpu_display_get_fb_info ever called with NULL tiling_flags/tmz_surface?
>>>> If not, there's no point in adding NULL checks.
>>> It isn't called with NULL anywhere, the NULL checks that already exist
>>> seem redundant.
>> Grigory, would be be willing to submit a v2 which removes the unnecessary
>> NULL checks?