Re: [Intel-gfx] [PATCH v5 1/6] drm/damage_helper: Check if damage clips has valid values

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Dec 14, 2020 at 09:27:30AM +0000, Mun, Gwan-gyeong wrote:
> On Mon, 2020-12-14 at 08:55 +0000, Simon Ser wrote:
> > > Userspace can set a damage clip with a negative coordinate,
> > > negative
> > > width or height or larger than the plane.
> > > This invalid values could cause issues in some HW or even worst
> > > enable
> > > security flaws.
> > > 
> > > v2:
> > > - add debug messages to let userspace know why atomic commit failed
> > > due invalid damage clips
> > > 
> > > Cc: Simon Ser <contact@emersion.fr>
> > > Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
> > > Cc: Sean Paul <seanpaul@chromium.org>
> > > Cc: Fabio Estevam <festevam@gmail.com>
> > > Cc: Deepak Rawat <drawat@vmware.com>
> > > Cc: dri-devel@lists.freedesktop.org
> > > Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> > 
> > After looking at the kernel code, it seems like the kernel already
> > checks for
> > all of that in drm_atomic_plane_check. Are you aware of this?
> > 
> > > +	w = drm_rect_width(&plane_state->src) >> 16;
> > > +	h = drm_rect_height(&plane_state->src) >> 16;
> > 
> > The docs say this should be in FB coordinates, not in SRC_*
> > coordinates. So we
> > shouldn't need to check any SRC_* prop here.
> > 
> I agree the Simon's opinion. it does check between plane's frame buffer
> src geometry and damage clips. (Plane's damage clip might exist outside
> of fb src geometry.)

Since this is causing confusion, please make sure that the igt for damage
clips validates this correctly. I think some of the igts that vmwgfx
people have created have still not yet landed, so we definitely want to
land these.

Note that basic damage clips tests should be fully generic, i.e. not tied
to anything driver specific like our psr testcases are.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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