linux-kernel - Re: [PATCH 1/2] drm/msm/dpu: Add NULL pointer check in dpu_crtc_duplicate

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Message-ID: <hl7op7zsxzmyttdjv2ijyutnobwjpl2fezaz7ohnlahzatui5y@677c4g676ekn>
Date: Sat, 13 Dec 2025 06:02:41 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: david@...t.cz
Cc: Rob Clark <robin.clark@....qualcomm.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jesszhan0024@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Bjorn Andersson <andersson@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Petr Hodina <petr.hodina@...tonmail.com>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, phone-devel@...r.kernel.org
Subject: Re: [PATCH 1/2] drm/msm/dpu: Add NULL pointer check in
 dpu_crtc_duplicate_state()

On Sat, Dec 13, 2025 at 12:08:16AM +0100, David Heidelberg via B4 Relay wrote:
> From: Petr Hodina <petr.hodina@...tonmail.com>
> 
> dpu_crtc_duplicate_state() assumes that crtc->state is always valid,
> but under certain error or teardown paths it may be NULL, leading to
> a NULL-pointer dereference when calling to_dpu_crtc_state().
> 
> Signed-off-by: Petr Hodina <petr.hodina@...tonmail.com>
> Signed-off-by: David Heidelberg <david@...t.cz>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)

Missing Fixes tag.

> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> index c39f1908ea654..d03666e14d7de 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> @@ -1114,7 +1114,12 @@ static void dpu_crtc_reset(struct drm_crtc *crtc)
>   */
>  static struct drm_crtc_state *dpu_crtc_duplicate_state(struct drm_crtc *crtc)
>  {
> -	struct dpu_crtc_state *cstate, *old_cstate = to_dpu_crtc_state(crtc->state);
> +	struct dpu_crtc_state *cstate, *old_cstate;
> +
> +	if (WARN_ON(!crtc->state))
> +		return NULL;
> +
> +	old_cstate = to_dpu_crtc_state(crtc->state);
>  
>  	cstate = kmemdup(old_cstate, sizeof(*old_cstate), GFP_KERNEL);
>  	if (!cstate) {
> 
> -- 
> 2.51.0
> 
> 

-- 
With best wishes
Dmitry