[PATCH 3.16 127/294] drm: Release driver tracking before making the object available again

[Ben Hutchings]

3.16.50-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

commit fe4600a548f2763dec91b3b27a1245c370ceee2a upstream.

This is the same bug as we fixed in commit f6cd7daecff5 ("drm: Release
driver references to handle before making it available again"), but now
the exposure is via the PRIME lookup tables. If we remove the
object/handle from the PRIME lut, then a new request for the same
object/fd will generate a new handle, thus for a short window that
object is known to userspace by two different handles. Fix this by
releasing the driver tracking before PRIME.

Fixes: 0ff926c7d4f0 ("drm/prime: add exported buffers to current fprivs
imported buffer list (v2)")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: Rob Clark <robdclark@xxxxxxxxx>
Cc: Ville SyrjÃlà <ville.syrjala@xxxxxxxxxxxxxxx>
Cc: Thierry Reding <treding@xxxxxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20170819120558.6465-1-chris@xxxxxxxxxxxxxxxxxx
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_gem.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -698,13 +698,13 @@ drm_gem_object_release_handle(int id, vo
 	struct drm_gem_object *obj = ptr;
 	struct drm_device *dev = obj->dev;
 
+	if (dev->driver->gem_close_object)
+		dev->driver->gem_close_object(obj, file_priv);
+
 	if (drm_core_check_feature(dev, DRIVER_PRIME))
 		drm_gem_remove_prime_handles(obj, file_priv);
 	drm_vma_node_revoke(&obj->vma_node, file_priv->filp);
 
-	if (dev->driver->gem_close_object)
-		dev->driver->gem_close_object(obj, file_priv);
-
 	drm_gem_object_handle_unreference_unlocked(obj);
 
 	return 0;