linux-kernel - Re: [PATCH] drm/msm/dpu: Add a null ptr check for dpu_encoder_needs

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Message-ID: <ciawdvjevycjjuowmykfux2v25lvr66kzey4jklq7t5cjzqalj@qfcva77k2bvr>
Date: Wed, 23 Jul 2025 22:05:00 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Chenyuan Yang <chenyuan0y@...il.com>
Cc: robin.clark@....qualcomm.com, lumag@...nel.org, abhinav.kumar@...ux.dev,
        jessica.zhang@....qualcomm.com, sean@...rly.run,
        marijn.suijten@...ainline.org, airlied@...il.com, simona@...ll.ch,
        tglx@...utronix.de, krzysztof.kozlowski@...aro.org,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/msm/dpu: Add a null ptr check for
 dpu_encoder_needs_modeset

On Tue, Jul 22, 2025 at 04:17:40PM -0500, Chenyuan Yang wrote:
> The drm_atomic_get_new_connector_state() can return NULL if the
> connector is not part of the atomic state. Add a check to prevent
> a NULL pointer dereference.
> 
> This follows the same pattern used in dpu_encoder_update_topology()
> within the same file, which checks for NULL before using conn_state.
> 
> Signed-off-by: Chenyuan Yang <chenyuan0y@...il.com>
> Fixes: 1ce69c265a53 ("drm/msm/dpu: move resource allocation to CRTC")
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index c0ed110a7d30..4bddb9504796 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -729,6 +729,8 @@ bool dpu_encoder_needs_modeset(struct drm_encoder *drm_enc, struct drm_atomic_st
>  		return false;
>  
>  	conn_state = drm_atomic_get_new_connector_state(state, connector);
> +	if (!conn_state)
> +		return false;

Did this happen in a real case or is it just
yet-another-static-analysys?

>  
>  	/**
>  	 * These checks are duplicated from dpu_encoder_update_topology() since
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry