Re: [PATCH v3 8/9] drm/rockchip: gem: Don't alloc/free gem buf when dev_private is invalid

From: Daniel Vetter <daniel@ffwll.ch>
To: Sean Paul <seanpaul@chromium.org>
Cc: Jeffy Chen <jeffy.chen@rock-chips.com>,
	dianders@chromium.org, briannorris@chromium.org,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	tfiga@chromium.org, linux-rockchip@lists.infradead.org,
	zyw@rock-chips.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 8/9] drm/rockchip: gem: Don't alloc/free gem buf when dev_private is invalid
Date: Thu, 6 Apr 2017 10:26:12 +0200	[thread overview]
Message-ID: <20170406082612.qmwyfjr5uwcp3arr@phenom.ffwll.local> (raw)
In-Reply-To: <20170405162839.k6q4b3tpt6t2s3zm@art_vandelay>

On Wed, Apr 05, 2017 at 12:28:40PM -0400, Sean Paul wrote:
> On Wed, Apr 05, 2017 at 04:29:26PM +0800, Jeffy Chen wrote:
> > After unbinding drm, the userspace may still has a chance to access
> > gem buf.
> > 
> > Add a sanity check for a NULL dev_private to prevent that from
> > happening.
> 
> I still don't understand how this is happening. You're saying that these hooks
> can be called after rockchip_drm_unbind() has finished? 

Yeah this is supposed to be impossible. If it isn't, we need to debug and
fix this properly. This smells like pretty bad duct-tape ...
-Daniel

> 
> Sean
> 
> > 
> > Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
> > ---
> > 
> > Changes in v3:
> > Address Daniel Vetter <daniel@ffwll.ch>'s comments.
> > Update commit message.
> > 
> > Changes in v2: None
> > 
> >  drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> > index df9e570..205a3dc 100644
> > --- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> > +++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
> > @@ -184,6 +184,9 @@ static int rockchip_gem_alloc_buf(struct rockchip_gem_object *rk_obj,
> >  	struct drm_device *drm = obj->dev;
> >  	struct rockchip_drm_private *private = drm->dev_private;
> >  
> > +	if (!private)
> > +		return -ENODEV;
> > +
> >  	if (private->domain)
> >  		return rockchip_gem_alloc_iommu(rk_obj, alloc_kmap);
> >  	else
> > @@ -208,6 +211,11 @@ static void rockchip_gem_free_dma(struct rockchip_gem_object *rk_obj)
> >  
> >  static void rockchip_gem_free_buf(struct rockchip_gem_object *rk_obj)
> >  {
> > +	struct drm_device *drm = rk_obj->base.dev;
> > +
> > +	if (!drm->dev_private)
> > +		return;
> > +
> >  	if (rk_obj->pages)
> >  		rockchip_gem_free_iommu(rk_obj);
> >  	else
> > -- 
> > 2.1.4
> > 
> 
> -- 
> Sean Paul, Software Engineer, Google / Chromium OS
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch