linux-kernel - Re: [PATCH] drm/bridge: Add null pointer check for ITE IT6263

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Message-ID: <20250723-gigantic-wrasse-of-warranty-dc70d7@houat>
Date: Wed, 23 Jul 2025 08:57:07 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Chenyuan Yang <chenyuan0y@...il.com>
Cc: victor.liu@....com, 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, lumag@...nel.org, biju.das.jz@...renesas.com, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/bridge: Add null pointer check for ITE IT6263

On Tue, Jul 22, 2025 at 03:41:14PM -0500, Chenyuan Yang wrote:
> drm_atomic_get_new_connector_for_encoder and
> drm_atomic_get_new_connector_state could return Null.

They can, but not in that scenario. atomic_enable will never be called
if either would return NULL.

In which situation did you trigger this bug?

> Thus, add the null pointer check for them with a similar format with
> it6505_bridge_atomic_enable in ITE IT6505.
> 
> Signed-off-by: Chenyuan Yang <chenyuan0y@...il.com>
> Fixes: 049723628716 ("drm/bridge: Add ITE IT6263 LVDS to HDMI converter")
> ---
>  drivers/gpu/drm/bridge/ite-it6263.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/ite-it6263.c b/drivers/gpu/drm/bridge/ite-it6263.c
> index a3a63a977b0a..3a20b2088bf9 100644
> --- a/drivers/gpu/drm/bridge/ite-it6263.c
> +++ b/drivers/gpu/drm/bridge/ite-it6263.c
> @@ -590,15 +590,28 @@ static void it6263_bridge_atomic_enable(struct drm_bridge *bridge,
>  	struct drm_connector *connector;
>  	bool is_stable = false;
>  	struct drm_crtc *crtc;
> +	struct drm_connector_state *conn_state;
>  	unsigned int val;
>  	bool pclk_high;
>  	int i, ret;
>  
>  	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;
> +
>  	mode = &crtc_state->adjusted_mode;
> +	if (WARN_ON(!mode))
> +		return;

And that condition can never be true.

Maxime

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