[PATCH v2 1/2] drm/amd/display: Add null check for 'afb' in amdgpu_dm_update_cursor (v2)

[Chung, ChiaHsuan (Tom)]

Reviewed-by: Tom Chung <chiahsuan.chung at amd.com>

On 8/7/2024 9:20 AM, Srinivasan Shanmugam wrote:
> This commit adds a null check for the 'afb' variable in the
> amdgpu_dm_update_cursor function. Previously, 'afb' was assumed to be
> null at line 8388, but was used later in the code without a null check.
> This could potentially lead to a null pointer dereference.
>
> Changes since v1:
> - Moved the null check for 'afb' to the line where 'afb' is used. (Alex)
>
> Fixes the below:
> drivers/gpu/drm/amd/amdgpu/../display/amdgpu_dm/amdgpu_dm.c:8433 amdgpu_dm_update_cursor()
> 	error: we previously assumed 'afb' could be null (see line 8388)
>
> Cc: Tom Chung <chiahsuan.chung at amd.com>
> Cc: Rodrigo Siqueira <Rodrigo.Siqueira at amd.com>
> Cc: Roman Li <roman.li at amd.com>
> Cc: Alex Hung <alex.hung at amd.com>
> Cc: Aurabindo Pillai <aurabindo.pillai at amd.com>
> Cc: Harry Wentland <harry.wentland at amd.com>
> Co-developed-by: Alex Hung <alex.hung at amd.com>
> Signed-off-by: Alex Hung <alex.hung at amd.com>
> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>
> ---
>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> 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 293f93d1976c..0fe043df643d 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -8697,7 +8697,8 @@ static void amdgpu_dm_update_cursor(struct drm_plane *plane,
>   	    adev->dm.dc->caps.color.dpp.gamma_corr)
>   		attributes.attribute_flags.bits.ENABLE_CURSOR_DEGAMMA = 1;
>   
> -	attributes.pitch = afb->base.pitches[0] / afb->base.format->cpp[0];
> +	if (afb)
> +		attributes.pitch = afb->base.pitches[0] / afb->base.format->cpp[0];
>   
>   	if (crtc_state->stream) {
>   		if (!dc_stream_set_cursor_attributes(crtc_state->stream,