[PATCH 1/2] drm/i915: Reject unknown syncobj flags

[Chris Wilson]

Quoting Tvrtko Ursulin (2017-10-31 10:23:25)
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> We have to reject unknown flags for uAPI considerations, and also
> because the curent implementation limits their i915 storage space
> to two bits.
> 
> v2: (Chris Wilson)
>  * Fix fail in ABI check.
>  * Added unknown flags and BUILD_BUG_ON.
> 
> v3:
>  * Use ARCH_KMALLOC_MINALIGN instead of alignof. (Chris Wilson)
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> Fixes: cf6e7bac6357 ("drm/i915: Add support for drm syncobjs")
> Cc: Jason Ekstrand <jason at jlekstrand.net>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: David Airlie <airlied at linux.ie>
> Cc: intel-gfx at lists.freedesktop.org
> Cc: dri-devel at lists.freedesktop.org
> ---
>  drivers/gpu/drm/i915/i915_gem_execbuffer.c | 8 ++++++++
>  include/uapi/drm/i915_drm.h                | 1 +
>  2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> index 3d7190764f10..a53be7d01055 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -2100,6 +2100,11 @@ get_fence_array(struct drm_i915_gem_execbuffer2 *args,
>                         goto err;
>                 }
>  
> +               if (fence.flags & __I915_EXEC_FENCE_UNKNOWN_FLAGS) {
> +                       err = -EINVAL;
> +                       goto err;
> +               }
> +
>                 syncobj = drm_syncobj_find(file, fence.handle);
>                 if (!syncobj) {
>                         DRM_DEBUG("Invalid syncobj handle provided\n");
> @@ -2107,6 +2112,9 @@ get_fence_array(struct drm_i915_gem_execbuffer2 *args,
>                         goto err;
>                 }
>  
> +               BUILD_BUG_ON(~(ARCH_KMALLOC_MINALIGN - 1) &
> +                            ~__I915_EXEC_FENCE_UNKNOWN_FLAGS);
> +
>                 fences[n] = ptr_pack_bits(syncobj, fence.flags, 2);

Was pondering how to tie the .n=2 into the BUILD_BUG_ON, but that
doesn't limit the improvement and fixes in this patch, so

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris