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

Daniel Vetter
2017-04-06T08:26:20Z

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