[Intel-gfx] [PATCH 3/5] drm/i915: Prevent writing into a read-only object via a GGTT mmap

[Chris Wilson]

Quoting Joonas Lahtinen (2018-06-15 09:08:54)
> Quoting Chris Wilson (2018-06-14 22:24:02)
> > 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 <chris at chris-wilson.co.uk>
> > Cc: Jon Bloomfield <jon.bloomfield at intel.com>
> > Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Cc: Matthew Auld <matthew.william.auld at gmail.com>
> > Cc: David Herrmann <dh.herrmann at gmail.com>
> > Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com> #v1
> > Reviewed-by: Matthew Auld <matthew.william.auld at gmail.com> #v1
> > Reviewed-by: Jon Bloomfield <jon.bloomfield at intel.com>
> 
> <SNIP>
> 
> > +++ b/drivers/gpu/drm/drm_gem.c
> > @@ -1036,6 +1036,11 @@ int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
> >                 return -EACCES;
> >         }
> >  
> > +       if (vma->vm_flags & VM_WRITE && node->readonly) {
> > +               drm_gem_object_put_unlocked(obj);
> > +               return -EINVAL;
> > +       }
> > +
> 
> Pretty sure you want to split this patch and Cc: dri-devel. With that,
> both are:

I thought I cc'ed dri-devel on the previous sending. (At least I thought
about it.) Besides until ttm differentiates between read/write access,
it's a moot point.
-Chris