1 files changed, 31 insertions, 11 deletions

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index adb9eda4fa1a..d47aa774d64b 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -308,23 +308,26 @@ int drm_gem_dumb_destroy(struct drm_file *file,
 EXPORT_SYMBOL(drm_gem_dumb_destroy);
 
 /**
- * Create a handle for this object. This adds a handle reference
- * to the object, which includes a regular reference count. Callers
- * will likely want to dereference the object afterwards.
+ * drm_gem_handle_create_tail - internal functions to create a handle
+ * 
+ * This expects the dev->object_name_lock to be held already and will drop it
+ * before returning. Used to avoid races in establishing new handles when
+ * importing an object from either an flink name or a dma-buf.
  */
 int
-drm_gem_handle_create(struct drm_file *file_priv,
-                       struct drm_gem_object *obj,
-                       u32 *handlep)
+drm_gem_handle_create_tail(struct drm_file *file_priv,
+                           struct drm_gem_object *obj,
+                           u32 *handlep)
 {
         struct drm_device *dev = obj->dev;
         int ret;
 
+        WARN_ON(!mutex_is_locked(&dev->object_name_lock));
+
         /*
          * Get the user-visible handle using idr.  Preload and perform
          * allocation under our spinlock.
          */
-        mutex_lock(&dev->object_name_lock);
         idr_preload(GFP_KERNEL);
         spin_lock(&file_priv->table_lock);
 
@@ -351,6 +354,21 @@ drm_gem_handle_create(struct drm_file *file_priv,
 
         return 0;
 }
+
+/**
+ * Create a handle for this object. This adds a handle reference
+ * to the object, which includes a regular reference count. Callers
+ * will likely want to dereference the object afterwards.
+ */
+int
+drm_gem_handle_create(struct drm_file *file_priv,
+                       struct drm_gem_object *obj,
+                       u32 *handlep)
+{
+        mutex_lock(&obj->dev->object_name_lock);
+
+        return drm_gem_handle_create_tail(file_priv, obj, handlep);
+}
 EXPORT_SYMBOL(drm_gem_handle_create);
 
 
@@ -627,13 +645,15 @@ drm_gem_open_ioctl(struct drm_device *dev, void *data,
 
         mutex_lock(&dev->object_name_lock);
         obj = idr_find(&dev->object_name_idr, (int) args->name);
-        if (obj)
+        if (obj) {
                 drm_gem_object_reference(obj);
-        mutex_unlock(&dev->object_name_lock);
-        if (!obj)
+        } else {
+                mutex_unlock(&dev->object_name_lock);
                 return -ENOENT;
+        }
 
-        ret = drm_gem_handle_create(file_priv, obj, &handle);
+        /* drm_gem_handle_create_tail unlocks dev->object_name_lock. */
+        ret = drm_gem_handle_create_tail(file_priv, obj, &handle);
         drm_gem_object_unreference_unlocked(obj);
         if (ret)
                 return ret;