Re: [PATCH] drm/msm/dpu: Add check for cstate

[Dmitry Baryshkov]

On 08/01/2023 23:56, Dmitry Baryshkov wrote:
> On 06/12/2022 10:05, Jiasheng Jiang wrote:
> > As kzalloc may fail and return NULL pointer,
> > it should be better to check cstate
> > in order to avoid the NULL pointer dereference
> > in __drm_atomic_helper_crtc_reset.
> >
> > Fixes: 1cff7440a86e ("drm/msm: Convert to using 
> > __drm_atomic_helper_crtc_reset() for reset.")
> > Signed-off-by: Jiasheng Jiang <jiasheng@xxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c 
> > b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > index 13ce321283ff..22c2787b7b38 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > @@ -968,7 +968,10 @@ static void dpu_crtc_reset(struct drm_crtc *crtc)
> >       if (crtc->state)
> >           dpu_crtc_destroy_state(crtc, crtc->state);
> > -    __drm_atomic_helper_crtc_reset(crtc, &cstate->base);
> > +    if (cstate)
> > +        __drm_atomic_helper_crtc_reset(crtc, &cstate->base);
> > +    else
> > +        __drm_atomic_helper_crtc_reset(crtc, NULL);
>
> NAK.
>
> The proper fix is to add the if() but to skip the else clause. We should 
> not reset the crtc's state if memory allocation failed.

On the other hand... Some of the drivers do exactly this ops.

With the message fixed:

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

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With best wishes
Dmitry