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

[Joonas Lahtinen]

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:

Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

Regards, Joonas