Quoting Bloomfield, Jon (2018-06-14 17:36:29)
> > -Original Message-
> > From: Chris Wilson
> > Sent: Thursday, June 14, 2018 9:07 AM
> > To: intel-...@lists.freedesktop.org
> > Cc: dri-devel@lists.freedesktop.org; Chris Wilson
> > ;
> > Bloomfield, Jon ; Joonas Lahtinen
> > ; Matthew Auld
> > ; David Herrmann
> >
> > Subject: [PATCH v2] drm/i915: Prevent writing into a read-only object via a
> > GGTT mmap
> >
> > If the user has created a read-only object, they should not be allowed
> > to circumvent the write protection by using a GGTT mmapping. Deny it.
> >
> > Also most machines do not support read-only GGTT PTEs, so again we have
> > to reject attempted writes. Fortunately, this is known a priori, so we
> > can at least reject in the call to create the mmap (with a sanity check
> > in the fault handler).
> >
> > v2: Check the vma->vm_flags during mmap() to allow readonly access.
> >
> > Signed-off-by: Chris Wilson
> > Cc: Jon Bloomfield
> > Cc: Joonas Lahtinen
> > Cc: Matthew Auld
> > Cc: David Herrmann
>
> Shame about the BUG_ON, but probably overkill to add code to suppress
> the RO flag just for mmap.
>
> Reviewed-by: Jon Bloomfield
Maybe one day with a PIN_RO, we can put it back in again.
Just a feeling of unease for shadowing cache_level on the vma. If only
we could just erase the history of doing cache_domain tracking.
-Chris
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