linux-kernel - Re: [PATCH] drm/bochs: Fix NULL dereference on atomic

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Date:   Mon, 11 Mar 2019 07:11:59 -0300
From:   Rodrigo Siqueira <rodrigosiqueiramelo@...il.com>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        virtualization@...ts.linux-foundation.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/bochs: Fix NULL dereference on atomic_disable helper

On 03/11, Gerd Hoffmann wrote:
> On Sun, Mar 10, 2019 at 06:21:50PM -0300, Rodrigo Siqueira wrote:
> > When the subtest basic-plain-flip from IGT project was executed on Bochs
> > driver, the following bug appears:
> > 
> > BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> 
> >  ? drm_atomic_helper_commit_modeset_disables+0x396/0x3e0 [drm_kms_helper]
> 
> > +static void  bochs_crtc_atomic_disable(struct drm_crtc *crtc,
> > +				       struct drm_crtc_state *old_state)
> > +{
> > +}
> > +
> >  static void bochs_crtc_atomic_flush(struct drm_crtc *crtc,
> >  				    struct drm_crtc_state *old_crtc_state)
> >  {
> > @@ -66,6 +71,7 @@ static const struct drm_crtc_funcs bochs_crtc_funcs = {
> >  static const struct drm_crtc_helper_funcs bochs_helper_funcs = {
> >  	.mode_set_nofb = bochs_crtc_mode_set_nofb,
> >  	.atomic_enable = bochs_crtc_atomic_enable,
> > +	.atomic_disable = bochs_crtc_atomic_disable,
> 
> Shouldn't we make the callback optional instead of adding empty dummy
> functions to drivers?

Hi Gerd,

I agree, and I can work in this issue.
Just one question, should we make atomic_enable optional as well?
 
Thanks for your feedback,
Best Regards
> cheers,
>   Gerd
> 

-- 
Rodrigo Siqueira
https://siqueira.tech
Graduate Student
Department of Computer Science
University of São Paulo

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