drm: fix locking in gem debugfs/procfs file

The idr is protected with our spinlock, if we don't hold that nothing
prevents the gem objects from disappearing from under us.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_info.c

@@ -218,7 +218,11 @@ int drm_gem_name_info(struct seq_file *m, void *data)
 	struct drm_device *dev = node->minor->dev;
 
 	seq_printf(m, "  name     size handles refcount\n");
+
+	spin_lock(&dev->object_name_lock);
 	idr_for_each(&dev->object_name_idr, drm_gem_one_name_info, m);
+	spin_unlock(&dev->object_name_lock);
+
 	return 0;
 }