1 files changed, 70 insertions, 26 deletions

diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c
index b59b26a71ad5..60a6b21474b1 100644
--- a/drivers/gpu/drm/drm_auth.c
+++ b/drivers/gpu/drm/drm_auth.c
@@ -52,7 +52,7 @@
  *
  * In addition only one &drm_master can be the current master for a &drm_device.
  * It can be switched through the DROP_MASTER and SET_MASTER IOCTL, or
- * implicitly through closing/openeing the primary device node. See also
+ * implicitly through closing/opening the primary device node. See also
  * drm_is_current_master().
  *
  * Clients can authenticate against the current master (if it matches their own)
@@ -61,6 +61,36 @@
  * trusted clients.
  */
 
+static bool drm_is_current_master_locked(struct drm_file *fpriv)
+{
+	lockdep_assert_once(lockdep_is_held(&fpriv->master_lookup_lock) ||
+			    lockdep_is_held(&fpriv->minor->dev->master_mutex));
+
+	return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;
+}
+
+/**
+ * drm_is_current_master - checks whether @priv is the current master
+ * @fpriv: DRM file private
+ *
+ * Checks whether @fpriv is current master on its device. This decides whether a
+ * client is allowed to run DRM_MASTER IOCTLs.
+ *
+ * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting
+ * - the current master is assumed to own the non-shareable display hardware.
+ */
+bool drm_is_current_master(struct drm_file *fpriv)
+{
+	bool ret;
+
+	spin_lock(&fpriv->master_lookup_lock);
+	ret = drm_is_current_master_locked(fpriv);
+	spin_unlock(&fpriv->master_lookup_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL(drm_is_current_master);
+
 int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv)
 {
 	struct drm_auth *auth = data;
@@ -135,16 +165,18 @@ static void drm_set_master(struct drm_device *dev, struct drm_file *fpriv,
 static int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv)
 {
 	struct drm_master *old_master;
+	struct drm_master *new_master;
 
 	lockdep_assert_held_once(&dev->master_mutex);
 
 	WARN_ON(fpriv->is_master);
 	old_master = fpriv->master;
-	fpriv->master = drm_master_create(dev);
-	if (!fpriv->master) {
-		fpriv->master = old_master;
+	new_master = drm_master_create(dev);
+	if (!new_master)
 		return -ENOMEM;
-	}
+	spin_lock(&fpriv->master_lookup_lock);
+	fpriv->master = new_master;
+	spin_unlock(&fpriv->master_lookup_lock);
 
 	fpriv->is_master = 1;
 	fpriv->authenticated = 1;
@@ -223,7 +255,7 @@ int drm_setmaster_ioctl(struct drm_device *dev, void *data,
 	if (ret)
 		goto out_unlock;
 
-	if (drm_is_current_master(file_priv))
+	if (drm_is_current_master_locked(file_priv))
 		goto out_unlock;
 
 	if (dev->master) {
@@ -272,7 +304,7 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data,
 	if (ret)
 		goto out_unlock;
 
-	if (!drm_is_current_master(file_priv)) {
+	if (!drm_is_current_master_locked(file_priv)) {
 		ret = -EINVAL;
 		goto out_unlock;
 	}
@@ -303,10 +335,13 @@ int drm_master_open(struct drm_file *file_priv)
 	 * any master object for render clients
 	 */
 	mutex_lock(&dev->master_mutex);
-	if (!dev->master)
+	if (!dev->master) {
 		ret = drm_new_set_master(dev, file_priv);
-	else
+	} else {
+		spin_lock(&file_priv->master_lookup_lock);
 		file_priv->master = drm_master_get(dev->master);
+		spin_unlock(&file_priv->master_lookup_lock);
+	}
 	mutex_unlock(&dev->master_mutex);
 
 	return ret;
@@ -322,7 +357,7 @@ void drm_master_release(struct drm_file *file_priv)
 	if (file_priv->magic)
 		idr_remove(&file_priv->master->magic_map, file_priv->magic);
 
-	if (!drm_is_current_master(file_priv))
+	if (!drm_is_current_master_locked(file_priv))
 		goto out;
 
 	drm_legacy_lock_master_cleanup(dev, master);
@@ -344,22 +379,6 @@ out:
 }
 
 /**
- * drm_is_current_master - checks whether @priv is the current master
- * @fpriv: DRM file private
- *
- * Checks whether @fpriv is current master on its device. This decides whether a
- * client is allowed to run DRM_MASTER IOCTLs.
- *
- * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting
- * - the current master is assumed to own the non-shareable display hardware.
- */
-bool drm_is_current_master(struct drm_file *fpriv)
-{
-	return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;
-}
-EXPORT_SYMBOL(drm_is_current_master);
-
-/**
  * drm_master_get - reference a master pointer
  * @master: &struct drm_master
  *
@@ -372,6 +391,31 @@ struct drm_master *drm_master_get(struct drm_master *master)
 }
 EXPORT_SYMBOL(drm_master_get);
 
+/**
+ * drm_file_get_master - reference &drm_file.master of @file_priv
+ * @file_priv: DRM file private
+ *
+ * Increments the reference count of @file_priv's &drm_file.master and returns
+ * the &drm_file.master. If @file_priv has no &drm_file.master, returns NULL.
+ *
+ * Master pointers returned from this function should be unreferenced using
+ * drm_master_put().
+ */
+struct drm_master *drm_file_get_master(struct drm_file *file_priv)
+{
+	struct drm_master *master = NULL;
+
+	spin_lock(&file_priv->master_lookup_lock);
+	if (!file_priv->master)
+		goto unlock;
+	master = drm_master_get(file_priv->master);
+
+unlock:
+	spin_unlock(&file_priv->master_lookup_lock);
+	return master;
+}
+EXPORT_SYMBOL(drm_file_get_master);
+
 static void drm_master_destroy(struct kref *kref)
 {
 	struct drm_master *master = container_of(kref, struct drm_master, refcount);