[PATCH 1/1] drm: mxsfb: Fix NULL pointer dereference

[Marek Vasut]

On 1/21/22 14:12, Alexander Stein wrote:
> Do not deference the NULL pointer if the bridge does not return a
> bridge state. Assume a fixed format instead.
> 
> Fixes: commit b776b0f00f24 ("drm: mxsfb: Use bus_format from the nearest bridge if present")
> Signed-off-by: Alexander Stein <alexander.stein at ew.tq-group.com>
> ---
> This can happen if a "ti,sn75lvds83", "lvds-encoder" bridge is attached
> to it. atomic_get_input_bus_fmts is only implemented for the
> lvds-decoder case.
> 
>   drivers/gpu/drm/mxsfb/mxsfb_kms.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> index 0655582ae8ed..4cfb6c001679 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
> @@ -361,7 +361,11 @@ static void mxsfb_crtc_atomic_enable(struct drm_crtc *crtc,
>   		bridge_state =
>   			drm_atomic_get_new_bridge_state(state,
>   							mxsfb->bridge);
> -		bus_format = bridge_state->input_bus_cfg.format;
> +		if (!bridge_state)
> +			bus_format = MEDIA_BUS_FMT_FIXED;
> +		else
> +			bus_format = bridge_state->input_bus_cfg.format;
> +
>   		if (bus_format == MEDIA_BUS_FMT_FIXED) {
>   			dev_warn_once(drm->dev,
>   				      "Bridge does not provide bus format, assuming MEDIA_BUS_FMT_RGB888_1X24.\n"


Shouldn't this be fixed on the bridge driver side instead ?

Which bridge driver do you use ?