[PATCH v2 1/3] drm/i915: Reject unknown syncobj flags

[Tvrtko Ursulin]

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.

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..58e994c4b5c7 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(~(__alignof__(void *) - 1) &
+			     ~__I915_EXEC_FENCE_UNKNOWN_FLAGS);
+
 		fences[n] = ptr_pack_bits(syncobj, fence.flags, 2);
 	}
 
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 125bde7d9504..ac3c6503ca27 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -839,6 +839,7 @@ struct drm_i915_gem_exec_fence {
 
 #define I915_EXEC_FENCE_WAIT            (1<<0)
 #define I915_EXEC_FENCE_SIGNAL          (1<<1)
+#define __I915_EXEC_FENCE_UNKNOWN_FLAGS (-(I915_EXEC_FENCE_SIGNAL << 1))
 	__u32 flags;
 };
 
-- 
2.9.5