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

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Message-ID: <2rtdf7azwluus757f3azwjacoiqussnoxfqqxtr3p3l4l7rkrt@dbk5pfdglugu>
Date: Wed, 13 Aug 2025 20:40:24 +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 Wed, Jul 23, 2025 at 12:43:06PM -0700, Chenyuan Yang wrote:
> On Wed, Jul 23, 2025 at 12:05 PM Dmitry Baryshkov
> <dmitry.baryshkov@....qualcomm.com> wrote:
> >
> > 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?
> 
> This is a static-analysis detected bug.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>



> 
> > >
> > >       /**
> > >        * These checks are duplicated from dpu_encoder_update_topology() since
> > > --
> > > 2.34.1
> > >
> >
> > --
> > With best wishes
> > Dmitry

-- 
With best wishes
Dmitry