linux-kernel - Re: [PATCH 2/2] drm/amd/display: Fix null pointer dereference in error message

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Date:   Wed, 27 Sep 2023 10:07:26 -0400
From:   Harry Wentland <harry.wentland@....com>
To:     Christian König <christian.koenig@....com>,
        Cong Liu <liucong2@...inos.cn>, Leo Li <sunpeng.li@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Aurabindo Pillai <aurabindo.pillai@....com>,
        Tom Chung <chiahsuan.chung@....com>
Cc:     amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] drm/amd/display: Fix null pointer dereference in
 error message



On 2023-09-27 01:23, Christian König wrote:
> Am 26.09.23 um 15:09 schrieb Harry Wentland:
>>
>> On 2023-09-26 01:56, Cong Liu wrote:
>>> This patch fixes a null pointer dereference in the error message that is
>>> printed when the Display Core (DC) fails to initialize. The original
>>> message includes the DC version number, which is undefined if the DC is
>>> not initialized.
>>>
>>> Fixes: 9788d087caff ("drm/amd/display: improve the message printed when loading DC")
>>> Signed-off-by: Cong Liu <liucong2@...inos.cn>
>>> ---
>>>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 +--
>>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>>> index 8e98dda1e084..bf52a909f558 100644
>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>>> @@ -1703,8 +1703,7 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
>>>           DRM_INFO("Display Core v%s initialized on %s\n", DC_VER,
>>>                dce_version_to_string(adev->dm.dc->ctx->dce_version));
>>>       } else {
>>> -        DRM_INFO("Display Core v%s failed to initialize on %s\n", DC_VER,
>>> -             dce_version_to_string(adev->dm.dc->ctx->dce_version));
>>> +        DRM_INFO("Display Core failed to initialize with v%s!\n", DC_VER);
>> There is value in printing the version number. Let's not remove it.
>>
>> Instead you can probably fix it by doing a NULL check on adev->dm.dc->ctx.
> 
> But as far as I understand it adev->dm.dc->ctx will always be NULL in this case.
> 

Thanks, Christian. We're in the else of the NULL check for
adev-dm.dc, so obviously we can't get the version. Silly me.

Your patch is
Reviewed-by: Harry Wentland <harry.wentland@....com>

Harry

> Regards,
> Christian.
> 
>>
>> Harry
>>
>>>           goto error;
>>>       }
>>>   
>