driver core: check start node in klist_iter_init_node

klist_iter_init_node() takes a node as a start argument.
However, this node might not be valid anymore.
This patch updates the klist_iter_init_node() and
dependent functions to return an error if so.
All calling functions have been audited to check
for a return code here.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Cc: Greg Kroah-Hartmann <gregkh@linuxfoundation.org>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Stable Kernel <stable@kernel.org>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/bus.c

@@ -296,11 +296,13 @@ int bus_for_each_dev(struct bus_type *bus, struct device *start,
 	if (!bus)
 		return -EINVAL;
 
-	klist_iter_init_node(&bus->p->klist_devices, &i,
+	error = klist_iter_init_node(&bus->p->klist_devices, &i,
 				     (start ? &start->p->knode_bus : NULL));
+	if (!error) {
 		while ((dev = next_device(&i)) && !error)
 			error = fn(dev, data);
 		klist_iter_exit(&i);
+	}
 	return error;
 }
 EXPORT_SYMBOL_GPL(bus_for_each_dev);
@@ -330,8 +332,10 @@ struct device *bus_find_device(struct bus_type *bus,
 	if (!bus)
 		return NULL;
 
-	klist_iter_init_node(&bus->p->klist_devices, &i,
-			     (start ? &start->p->knode_bus : NULL));
+	if (klist_iter_init_node(&bus->p->klist_devices, &i,
+				 (start ? &start->p->knode_bus : NULL)) < 0)
+		return NULL;
+
 	while ((dev = next_device(&i)))
 		if (match(dev, data) && get_device(dev))
 			break;
@@ -384,7 +388,9 @@ struct device *subsys_find_device_by_id(struct bus_type *subsys, unsigned int id
 		return NULL;
 
 	if (hint) {
-		klist_iter_init_node(&subsys->p->klist_devices, &i, &hint->p->knode_bus);
+		if (klist_iter_init_node(&subsys->p->klist_devices, &i,
+					 &hint->p->knode_bus) < 0)
+			return NULL;
 		dev = next_device(&i);
 		if (dev && dev->id == id && get_device(dev)) {
 			klist_iter_exit(&i);
@@ -446,11 +452,13 @@ int bus_for_each_drv(struct bus_type *bus, struct device_driver *start,
 	if (!bus)
 		return -EINVAL;
 
-	klist_iter_init_node(&bus->p->klist_drivers, &i,
+	error = klist_iter_init_node(&bus->p->klist_drivers, &i,
 				     start ? &start->p->knode_bus : NULL);
+	if (!error) {
 		while ((drv = next_driver(&i)) && !error)
 			error = fn(drv, data);
 		klist_iter_exit(&i);
+	}
 	return error;
 }
 EXPORT_SYMBOL_GPL(bus_for_each_drv);
@@ -1111,15 +1119,19 @@ EXPORT_SYMBOL_GPL(bus_sort_breadthfirst);
  * otherwise if it is NULL, the iteration starts at the beginning of
  * the list.
  */
-void subsys_dev_iter_init(struct subsys_dev_iter *iter, struct bus_type *subsys,
+int subsys_dev_iter_init(struct subsys_dev_iter *iter, struct bus_type *subsys,
 			 struct device *start, const struct device_type *type)
 {
 	struct klist_node *start_knode = NULL;
+	int error;
 
 	if (start)
 		start_knode = &start->p->knode_bus;
-	klist_iter_init_node(&subsys->p->klist_devices, &iter->ki, start_knode);
+	error = klist_iter_init_node(&subsys->p->klist_devices, &iter->ki,
+				     start_knode);
+	if (!error)
 		iter->type = type;
+	return error;
 }
 EXPORT_SYMBOL_GPL(subsys_dev_iter_init);
 

drivers/base/class.c

@@ -301,15 +301,20 @@ void class_destroy(struct class *cls)
  * otherwise if it is NULL, the iteration starts at the beginning of
  * the list.
  */
-void class_dev_iter_init(struct class_dev_iter *iter, struct class *class,
+int class_dev_iter_init(struct class_dev_iter *iter, struct class *class,
 			struct device *start, const struct device_type *type)
 {
 	struct klist_node *start_knode = NULL;
+	int error;
 
 	if (start)
 		start_knode = &start->knode_class;
-	klist_iter_init_node(&class->p->klist_devices, &iter->ki, start_knode);
+	error = klist_iter_init_node(&class->p->klist_devices, &iter->ki,
+				     start_knode);
+	if (!error)
 		iter->type = type;
+
+	return error;
 }
 EXPORT_SYMBOL_GPL(class_dev_iter_init);
 
@@ -387,14 +392,15 @@ int class_for_each_device(struct class *class, struct device *start,
 		return -EINVAL;
 	}
 
-	class_dev_iter_init(&iter, class, start, NULL);
+	error = class_dev_iter_init(&iter, class, start, NULL);
+	if (!error) {
 		while ((dev = class_dev_iter_next(&iter))) {
 			error = fn(dev, data);
 			if (error)
 				break;
 		}
 		class_dev_iter_exit(&iter);
-
+	}
 	return error;
 }
 EXPORT_SYMBOL_GPL(class_for_each_device);
@@ -434,7 +440,9 @@ struct device *class_find_device(struct class *class, struct device *start,
 		return NULL;
 	}
 
-	class_dev_iter_init(&iter, class, start, NULL);
+	if (class_dev_iter_init(&iter, class, start, NULL) < 0)
+		return NULL;
+
 	while ((dev = class_dev_iter_next(&iter))) {
 		if (match(dev, data)) {
 			get_device(dev);

drivers/base/driver.c

@@ -49,11 +49,13 @@ int driver_for_each_device(struct device_driver *drv, struct device *start,
 	if (!drv)
 		return -EINVAL;
 
-	klist_iter_init_node(&drv->p->klist_devices, &i,
+	error = klist_iter_init_node(&drv->p->klist_devices, &i,
 				     start ? &start->p->knode_driver : NULL);
+	if (!error) {
 		while ((dev = next_device(&i)) && !error)
 			error = fn(dev, data);
 		klist_iter_exit(&i);
+	}
 	return error;
 }
 EXPORT_SYMBOL_GPL(driver_for_each_device);
@@ -83,8 +85,10 @@ struct device *driver_find_device(struct device_driver *drv,
 	if (!drv)
 		return NULL;
 
-	klist_iter_init_node(&drv->p->klist_devices, &i,
-			     (start ? &start->p->knode_driver : NULL));
+	if (klist_iter_init_node(&drv->p->klist_devices, &i,
+				 (start ? &start->p->knode_driver : NULL)) < 0)
+		return NULL;
+
 	while ((dev = next_device(&i)))
 		if (match(dev, data) && get_device(dev))
 			break;

include/linux/device.h

@@ -128,7 +128,7 @@ struct subsys_dev_iter {
 	struct klist_iter		ki;
 	const struct device_type	*type;
 };
-void subsys_dev_iter_init(struct subsys_dev_iter *iter,
+int subsys_dev_iter_init(struct subsys_dev_iter *iter,
 			 struct bus_type *subsys,
 			 struct device *start,
 			 const struct device_type *type);
@@ -380,7 +380,7 @@ int class_compat_create_link(struct class_compat *cls, struct device *dev,
 void class_compat_remove_link(struct class_compat *cls, struct device *dev,
 			      struct device *device_link);
 
-extern void class_dev_iter_init(struct class_dev_iter *iter,
+extern int class_dev_iter_init(struct class_dev_iter *iter,
 			       struct class *class,
 			       struct device *start,
 			       const struct device_type *type);

include/linux/klist.h

@@ -60,7 +60,7 @@ struct klist_iter {
 
 
 extern void klist_iter_init(struct klist *k, struct klist_iter *i);
-extern void klist_iter_init_node(struct klist *k, struct klist_iter *i,
+extern int klist_iter_init_node(struct klist *k, struct klist_iter *i,
 				 struct klist_node *n);
 extern void klist_iter_exit(struct klist_iter *i);
 extern struct klist_node *klist_next(struct klist_iter *i);

lib/klist.c

@@ -278,13 +278,19 @@ EXPORT_SYMBOL_GPL(klist_node_attached);
  * Similar to klist_iter_init(), but starts the action off with @n,
  * instead of with the list head.
  */
-void klist_iter_init_node(struct klist *k, struct klist_iter *i,
+int klist_iter_init_node(struct klist *k, struct klist_iter *i,
 			 struct klist_node *n)
 {
+	if (n) {
+		kref_get(&n->n_ref);
+		if (!n->n_klist) {
+			kref_put(&n->n_ref);
+			return -ENODEV;
+		}
+	}
 	i->i_klist = k;
 	i->i_cur = n;
-	if (n)
-		kref_get(&n->n_ref);
+	return 0;
 }
 EXPORT_SYMBOL_GPL(klist_iter_init_node);