drm/i915: Reject unknown syncobj flags

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@intel.com>
Fixes: cf6e7bac6357 ("drm/i915: Add support for drm syncobjs")
Cc: Jason Ekstrand <jason@jlekstrand.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: David Airlie <airlied@linux.ie>
Cc: intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171031102326.9738-1-tvrtko.ursulin@linux.intel.com
(cherry picked from commit ebcaa1ff8b59097805d548fe7a676f194625c033)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

2 files changed, 9 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 4ac454ae54d7..83876a1c8d98 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -2094,6 +2094,11 @@ 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");
@@ -2101,6 +2106,9 @@ 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);
         }
 
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 6598fb76d2c2..9816590d3ad2 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -829,6 +829,7 @@ 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;
 };