Re: [PATCH 5/5] drm/mediatek: Fix dereference before null check

[CK Hu (胡俊光)]

Hi, Jason:

On Fri, 2023-04-07 at 14:46 +0800, Jason-JH.Lin wrote:
> Null-checking state suggests that it may be null, but it has already
> been dereferenced on drm_atomic_get_new_plane_state(state, plane).
> 
> The parameter state will never be NULL currently, so just remove the
> state is NULL flow in this function.
> 
> Signed-off-by: Jason-JH.Lin <jason-jh.lin@xxxxxxxxxxxx>
> Fixes: 5ddb0bd4ddc3 ("drm/atomic: Pass the full state to planes async
> atomic check and update")
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_plane.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> b/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> index a1337f386bbf..e14b2920d242 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_plane.c
> @@ -103,8 +103,7 @@ static void mtk_drm_plane_destroy_state(struct
> drm_plane *plane,
>  static int mtk_plane_atomic_async_check(struct drm_plane *plane,
>  					struct drm_atomic_state *state)
>  {
> -	struct drm_plane_state *new_plane_state =
> drm_atomic_get_new_plane_state(state,
> -									
> 	 plane);
> +	struct drm_plane_state *new_plane_state =
> drm_atomic_get_new_plane_state(state, plane);

This is not related to this patch, so move to another patch.

Regards,
CK

>  	struct drm_crtc_state *crtc_state;
>  	int ret;
>  
> @@ -122,11 +121,7 @@ static int mtk_plane_atomic_async_check(struct
> drm_plane *plane,
>  	if (ret)
>  		return ret;
>  
> -	if (state)
> -		crtc_state = drm_atomic_get_existing_crtc_state(state,
> -								new_pla
> ne_state->crtc);
> -	else /* Special case for asynchronous cursor updates. */
> -		crtc_state = new_plane_state->crtc->state;
> +	crtc_state = drm_atomic_get_existing_crtc_state(state,
> new_plane_state->crtc);
>  
>  	return drm_atomic_helper_check_plane_state(plane->state,
> crtc_state,
>  						   DRM_PLANE_NO_SCALING
> ,