linux-kernel - Re: [PATCH] drm/bridge: lt9211: Add null pointer check for LT9211

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Message-ID: <20250723-upbeat-seahorse-of-joy-eb8c9d@houat>
Date: Wed, 23 Jul 2025 08:58:38 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Chenyuan Yang <chenyuan0y@...il.com>
Cc: andrzej.hajda@...el.com, neil.armstrong@...aro.org, rfoss@...nel.org, 
	laurent.pinchart@...asonboard.com, jonas@...boo.se, jernej.skrabec@...il.com, 
	maarten.lankhorst@...ux.intel.com, tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/bridge: lt9211: Add null pointer check for LT9211

On Tue, Jul 22, 2025 at 03:57:12PM -0500, Chenyuan Yang wrote:
> drm_atomic_get_new_connector_for_encoder and
> drm_atomic_get_new_connector_state could return Null.
> Thus, add the null pointer check for them with a similar format with
> lt9611_bridge_atomic_enable in LT9611.
> 
> Signed-off-by: Chenyuan Yang <chenyuan0y@...il.com>
> ---
>  drivers/gpu/drm/bridge/lontium-lt9211.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/lontium-lt9211.c b/drivers/gpu/drm/bridge/lontium-lt9211.c
> index 9b2dac9bd63c..6be30c8bdf15 100644
> --- a/drivers/gpu/drm/bridge/lontium-lt9211.c
> +++ b/drivers/gpu/drm/bridge/lontium-lt9211.c
> @@ -463,6 +463,7 @@ static void lt9211_atomic_enable(struct drm_bridge *bridge,
>  	const struct drm_crtc_state *crtc_state;
>  	const struct drm_display_mode *mode;
>  	struct drm_connector *connector;
> +	struct drm_connector_state *conn_state;
>  	struct drm_crtc *crtc;
>  	bool lvds_format_24bpp;
>  	bool lvds_format_jeida;
> @@ -516,8 +517,18 @@ static void lt9211_atomic_enable(struct drm_bridge *bridge,
>  	 */
>  	connector = drm_atomic_get_new_connector_for_encoder(state,
>  							     bridge->encoder);
> -	crtc = drm_atomic_get_new_connector_state(state, connector)->crtc;
> +	if (WARN_ON(!connector))
> +		return;
> +
> +	conn_state = drm_atomic_get_new_connector_state(state, connector);
> +	if (WARN_ON(!conn_state))
> +		return;
> +
> +	crtc = conn_state->crtc;
>  	crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
> +	if (WARN_ON(!crtc_state))
> +		return;
> +

Ditto, that condition is never supposed to happen. How did you notice that bug?

Maxime

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