linux-kernel - Re: [PATCH v2] drm/amd/display: fix NULL dereference

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Message-ID: <689f3862-09d5-448d-b418-fd52d7288106@amd.com>
Date:   Tue, 14 Nov 2023 16:01:14 -0500
From:   Hamza Mahfooz <hamza.mahfooz@....com>
To:     José Pekkarinen <jose.pekkarinen@...hound.fi>,
        harry.wentland@....com, sunpeng.li@....com,
        Rodrigo.Siqueira@....com, alexander.deucher@....com,
        christian.koenig@....com, Xinhui.Pan@....com,
        skhan@...uxfoundation.org
Cc:     airlied@...il.com, daniel@...ll.ch, Wayne.Lin@....com,
        qingqing.zhuo@....com, lyude@...hat.com,
        srinivasan.shanmugam@....com, aurabindo.pillai@....com,
        sungjoon.kim@....com, wenjing.liu@....com, mikita.lipski@....com,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-kernel-mentees@...ts.linux.dev
Subject: Re: [PATCH v2] drm/amd/display: fix NULL dereference

On 11/14/23 10:27, José Pekkarinen wrote:
> The following patch will fix a minor issue where a debug message is
> referencing an struct that has just being checked whether is null or
> not. This has been noticed by using coccinelle, in the following output:
> 
> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c:540:25-29: ERROR: aconnector is NULL but dereferenced.
> 
> Fixes: 5d72e247e58c9 ("drm/amd/display: switch DC over to the new DRM logging macros")

You only need the first 12 characters of the hash here. I have fixed it
for you and applied the patch in this case. But, in the future please
test your patches against `./scripts/checkpatch.pl` before submitting
them.

> Signed-off-by: José Pekkarinen <jose.pekkarinen@...hound.fi>
> ---
> [v1 -> v2]: Remove the debugging message, requested by Hamza
> 
>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 5 +----
>   1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> index ed784cf27d39..c7a29bb737e2 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
> @@ -536,11 +536,8 @@ bool dm_helpers_dp_read_dpcd(
>   
>   	struct amdgpu_dm_connector *aconnector = link->priv;
>   
> -	if (!aconnector) {
> -		drm_dbg_dp(aconnector->base.dev,
> -			   "Failed to find connector for link!\n");
> +	if (!aconnector)
>   		return false;
> -	}
>   
>   	return drm_dp_dpcd_read(&aconnector->dm_dp_aux.aux, address, data,
>   				size) == size;
-- 
Hamza