Merge tag 'driver-core-5.13-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

Pull driver core fixes from Greg KH:
 "Here are three small driver core / debugfs fixes for 5.13-rc4:

   - debugfs fix for incorrect "lockdown" mode for selinux accesses

   - two device link changes, one bugfix and one cleanup

  All of these have been in linux-next for over a week with no reported
  problems"

* tag 'driver-core-5.13-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
  drivers: base: Reduce device link removal code duplication
  drivers: base: Fix device link removal
  debugfs: fix security_locked_down() call for SELinux

Author: torvalds

drivers/base/core.c

@@ -194,6 +194,17 @@ int device_links_read_lock_held(void)
 {
 	return srcu_read_lock_held(&device_links_srcu);
 }
+
+static void device_link_synchronize_removal(void)
+{
+	synchronize_srcu(&device_links_srcu);
+}
+
+static void device_link_remove_from_lists(struct device_link *link)
+{
+	list_del_rcu(&link->s_node);
+	list_del_rcu(&link->c_node);
+}
 #else /* !CONFIG_SRCU */
 static DECLARE_RWSEM(device_links_lock);
 
@@ -224,6 +235,16 @@ int device_links_read_lock_held(void)
 	return lockdep_is_held(&device_links_lock);
 }
 #endif
+
+static inline void device_link_synchronize_removal(void)
+{
+}
+
+static void device_link_remove_from_lists(struct device_link *link)
+{
+	list_del(&link->s_node);
+	list_del(&link->c_node);
+}
 #endif /* !CONFIG_SRCU */
 
 static bool device_is_ancestor(struct device *dev, struct device *target)
@@ -445,8 +466,13 @@ static struct attribute *devlink_attrs[] = {
 };
 ATTRIBUTE_GROUPS(devlink);
 
-static void device_link_free(struct device_link *link)
+static void device_link_release_fn(struct work_struct *work)
 {
+	struct device_link *link = container_of(work, struct device_link, rm_work);
+
+	/* Ensure that all references to the link object have been dropped. */
+	device_link_synchronize_removal();
+
 	while (refcount_dec_not_one(&link->rpm_active))
 		pm_runtime_put(link->supplier);
 
@@ -455,24 +481,19 @@ static void device_link_free(struct device_link *link)
 	kfree(link);
 }
 
-#ifdef CONFIG_SRCU
-static void __device_link_free_srcu(struct rcu_head *rhead)
-{
-	device_link_free(container_of(rhead, struct device_link, rcu_head));
-}
-
 static void devlink_dev_release(struct device *dev)
 {
 	struct device_link *link = to_devlink(dev);
 
-	call_srcu(&device_links_srcu, &link->rcu_head, __device_link_free_srcu);
-}
-#else
-static void devlink_dev_release(struct device *dev)
-{
-	device_link_free(to_devlink(dev));
+	INIT_WORK(&link->rm_work, device_link_release_fn);
+	/*
+	 * It may take a while to complete this work because of the SRCU
+	 * synchronization in device_link_release_fn() and if the consumer or
+	 * supplier devices get deleted when it runs, so put it into the "long"
+	 * workqueue.
+	 */
+	queue_work(system_long_wq, &link->rm_work);
 }
-#endif
 
 static struct class devlink_class = {
 	.name = "devlink",
@@ -846,7 +867,6 @@ struct device_link *device_link_add(struct device *consumer,
 }
 EXPORT_SYMBOL_GPL(device_link_add);
 
-#ifdef CONFIG_SRCU
 static void __device_link_del(struct kref *kref)
 {
 	struct device_link *link = container_of(kref, struct device_link, kref);
@@ -856,25 +876,9 @@ static void __device_link_del(struct kref *kref)
 
 	pm_runtime_drop_link(link);
 
-	list_del_rcu(&link->s_node);
-	list_del_rcu(&link->c_node);
-	device_unregister(&link->link_dev);
-}
-#else /* !CONFIG_SRCU */
-static void __device_link_del(struct kref *kref)
-{
-	struct device_link *link = container_of(kref, struct device_link, kref);
-
-	dev_info(link->consumer, "Dropping the link to %s\n",
-		 dev_name(link->supplier));
-
-	pm_runtime_drop_link(link);
-
-	list_del(&link->s_node);
-	list_del(&link->c_node);
+	device_link_remove_from_lists(link);
 	device_unregister(&link->link_dev);
 }
-#endif /* !CONFIG_SRCU */
 
 static void device_link_put_kref(struct device_link *link)
 {

fs/debugfs/inode.c

@@ -45,10 +45,13 @@ static unsigned int debugfs_allow __ro_after_init = DEFAULT_DEBUGFS_ALLOW_BITS;
 static int debugfs_setattr(struct user_namespace *mnt_userns,
 			   struct dentry *dentry, struct iattr *ia)
 {
-	int ret = security_locked_down(LOCKDOWN_DEBUGFS);
+	int ret;
 
-	if (ret && (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)))
-		return ret;
+	if (ia->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) {
+		ret = security_locked_down(LOCKDOWN_DEBUGFS);
+		if (ret)
+			return ret;
+	}
 	return simple_setattr(&init_user_ns, dentry, ia);
 }
 

include/linux/device.h

@@ -570,7 +570,7 @@ struct device {
  * @flags: Link flags.
  * @rpm_active: Whether or not the consumer device is runtime-PM-active.
  * @kref: Count repeated addition of the same link.
- * @rcu_head: An RCU head to use for deferred execution of SRCU callbacks.
+ * @rm_work: Work structure used for removing the link.
  * @supplier_preactivated: Supplier has been made active before consumer probe.
  */
 struct device_link {
@@ -583,9 +583,7 @@ struct device_link {
 	u32 flags;
 	refcount_t rpm_active;
 	struct kref kref;
-#ifdef CONFIG_SRCU
-	struct rcu_head rcu_head;
-#endif
+	struct work_struct rm_work;
 	bool supplier_preactivated; /* Owned by consumer probe. */
 };