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

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Date:   Tue, 26 Sep 2023 09:09:56 -0400
From:   Harry Wentland <harry.wentland@....com>
To:     Cong Liu <liucong2@...inos.cn>, Leo Li <sunpeng.li@....com>,
        Rodrigo Siqueira <Rodrigo.Siqueira@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....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 2023-09-26 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.

Harry

>  		goto error;
>  	}
>