[RESEND,V2] drm: fsl-dcu: Fix no fb check bug

[Emil Velikov]

Hi guys,

Am I loosing the plot here or something feels amiss here ?

On 6 January 2016 at 06:12, Meng Yi <meng.yi at nxp.com> wrote:
> For state->fb or state->crtc may be NULL in fsl_dcu_drm_plane_atomic_check
> function, if so, return 0.
>
> Signed-off-by: Meng Yi <meng.yi at nxp.com>
> Signed-off-by: Jianwei Wang <jianwei.wang.chn at gmail.com>
>
> ---
>
> change in v2:
> -Add state->crtc check
> -return 0 when state->fb or state->crtc is NULL, instead of -EINVAL
> Adviced by Daniel Stone
>
>  drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_plane.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_plane.c b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_plane.c
> index 4b13cf9..8965580 100644
> --- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_plane.c
> +++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_plane.c
> @@ -41,6 +41,9 @@ static int fsl_dcu_drm_plane_atomic_check(struct drm_plane *plane,
>  {
>         struct drm_framebuffer *fb = state->fb;
>
> +       if (!state->fb || !state->crtc)
> +               return 0;
> +
Namely: if we return success here core drm will end up calling the
atomic_update...

>         switch (fb->pixel_format) {
>         case DRM_FORMAT_RGB565:
>         case DRM_FORMAT_RGB888:
> @@ -85,9 +88,6 @@ static void fsl_dcu_drm_plane_atomic_update(struct drm_plane *plane,
>         unsigned int alpha, bpp;
>         int index, ret;
>
> -       if (!fb)
> -               return;
> -
... which no longer has the !fb check, and we'll crash with null deref
a few lines below ?

-Emil