ACPI / hotplug: Fix concurrency issues and memory leaks

This changeset is aimed at fixing a few different but related
problems in the ACPI hotplug infrastructure.

First of all, since notify handlers may be run in parallel with
acpi_bus_scan(), acpi_bus_trim() and acpi_bus_hot_remove_device()
and some of them are installed for ACPI handles that have no struct
acpi_device objects attached (i.e. before those objects are created),
those notify handlers have to take acpi_scan_lock to prevent races
from taking place (e.g. a struct acpi_device is found to be present
for the given ACPI handle, but right after that it is removed by
acpi_bus_trim() running in parallel to the given notify handler).
Moreover, since some of them call acpi_bus_scan() and
acpi_bus_trim(), this leads to the conclusion that acpi_scan_lock
should be acquired by the callers of these two funtions rather by
these functions themselves.

For these reasons, make all notify handlers that can handle device
addition and eject events take acpi_scan_lock and remove the
acpi_scan_lock locking from acpi_bus_scan() and acpi_bus_trim().
Accordingly, update all of their users to make sure that they
are always called under acpi_scan_lock.

Furthermore, since eject operations are carried out asynchronously
with respect to the notify events that trigger them, with the help
of acpi_bus_hot_remove_device(), even if notify handlers take the
ACPI scan lock, it still is possible that, for example,
acpi_bus_trim() will run between acpi_bus_hot_remove_device() and
the notify handler that scheduled its execution and that
acpi_bus_trim() will remove the device node passed to
acpi_bus_hot_remove_device() for ejection.  In that case, the struct
acpi_device object obtained by acpi_bus_hot_remove_device() will be
invalid and not-so-funny things will ensue.  To protect agaist that,
make the users of acpi_bus_hot_remove_device() run get_device() on
ACPI device node objects that are about to be passed to it and make
acpi_bus_hot_remove_device() run put_device() on them and check if
their ACPI handles are not NULL (make acpi_device_unregister() clear
the device nodes' ACPI handles for that check to work).

Finally, observe that acpi_os_hotplug_execute() actually can fail,
in which case its caller ought to free memory allocated for the
context object to prevent leaks from happening.  It also needs to
run put_device() on the device node that it ran get_device() on
previously in that case.  Modify the code accordingly.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Yinghai Lu <yinghai@kernel.org>

5 files changed, 126 insertions, 54 deletions

diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index 94c823b..034d3e7 100644
--- a/drivers/acpi/acpi_memhotplug.c
+++ b/drivers/acpi/acpi_memhotplug.c
@@ -153,14 +153,16 @@ acpi_memory_get_device_resources(struct acpi_memory_device *mem_device)
 	return 0;
 }
 
-static int
-acpi_memory_get_device(acpi_handle handle,
-		       struct acpi_memory_device **mem_device)
+static int acpi_memory_get_device(acpi_handle handle,
+				  struct acpi_memory_device **mem_device)
 {
 	struct acpi_device *device = NULL;
-	int result;
+	int result = 0;
 
-	if (!acpi_bus_get_device(handle, &device) && device)
+	acpi_scan_lock_acquire();
+
+	acpi_bus_get_device(handle, &device);
+	if (device)
 		goto end;
 
 	/*
@@ -169,23 +171,28 @@ acpi_memory_get_device(acpi_handle handle,
 	 */
 	result = acpi_bus_scan(handle);
 	if (result) {
-		acpi_handle_warn(handle, "Cannot add acpi bus\n");
-		return -EINVAL;
+		acpi_handle_warn(handle, "ACPI namespace scan failed\n");
+		result = -EINVAL;
+		goto out;
 	}
 	result = acpi_bus_get_device(handle, &device);
 	if (result) {
 		acpi_handle_warn(handle, "Missing device object\n");
-		return -EINVAL;
+		result = -EINVAL;
+		goto out;
 	}
 
-      end:
+ end:
 	*mem_device = acpi_driver_data(device);
 	if (!(*mem_device)) {
 		dev_err(&device->dev, "driver data not found\n");
-		return -ENODEV;
+		result = -ENODEV;
+		goto out;
 	}
 
-	return 0;
+ out:
+	acpi_scan_lock_release();
+	return result;
 }
 
 static int acpi_memory_check_device(struct acpi_memory_device *mem_device)
@@ -305,6 +312,7 @@ static void acpi_memory_device_notify(acpi_handle handle, u32 event, void *data)
 	struct acpi_device *device;
 	struct acpi_eject_event *ej_event = NULL;
 	u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; /* default */
+	acpi_status status;
 
 	switch (event) {
 	case ACPI_NOTIFY_BUS_CHECK:
@@ -327,29 +335,40 @@ static void acpi_memory_device_notify(acpi_handle handle, u32 event, void *data)
 		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 				  "\nReceived EJECT REQUEST notification for device\n"));
 
+		status = AE_ERROR;
+		acpi_scan_lock_acquire();
+
 		if (acpi_bus_get_device(handle, &device)) {
 			acpi_handle_err(handle, "Device doesn't exist\n");
-			break;
+			goto unlock;
 		}
 		mem_device = acpi_driver_data(device);
 		if (!mem_device) {
 			acpi_handle_err(handle, "Driver Data is NULL\n");
-			break;
+			goto unlock;
 		}
 
 		ej_event = kmalloc(sizeof(*ej_event), GFP_KERNEL);
 		if (!ej_event) {
 			pr_err(PREFIX "No memory, dropping EJECT\n");
-			break;
+			goto unlock;
 		}
 
+		get_device(&device->dev);
 		ej_event->device = device;
 		ej_event->event = ACPI_NOTIFY_EJECT_REQUEST;
-		acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
-					(void *)ej_event);
+		/* The eject is carried out asynchronously. */
+		status = acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
+						 ej_event);
+		if (ACPI_FAILURE(status)) {
+			put_device(&device->dev);
+			kfree(ej_event);
+		}
 
-		/* eject is performed asynchronously */
-		return;
+ unlock:
+		acpi_scan_lock_release();
+		if (ACPI_SUCCESS(status))
+			return;
 	default:
 		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 				  "Unsupported event [0x%x]\n", event));
@@ -360,7 +379,6 @@ static void acpi_memory_device_notify(acpi_handle handle, u32 event, void *data)
 
 	/* Inform firmware that the hotplug operation has completed */
 	(void) acpi_evaluate_hotplug_ost(handle, event, ost_code, NULL);
-	return;
 }
 
 static void acpi_memory_device_free(struct acpi_memory_device *mem_device)
diff --git a/drivers/acpi/container.c b/drivers/acpi/container.c
index 4cc2937..5523ba7 100644
--- a/drivers/acpi/container.c
+++ b/drivers/acpi/container.c
@@ -88,6 +88,8 @@ static void container_notify_cb(acpi_handle handle, u32 type, void *context)
 	acpi_status status;
 	u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; /* default */
 
+	acpi_scan_lock_acquire();
+
 	switch (type) {
 	case ACPI_NOTIFY_BUS_CHECK:
 		/* Fall through */
@@ -103,7 +105,7 @@ static void container_notify_cb(acpi_handle handle, u32 type, void *context)
 				/* device exist and this is a remove request */
 				device->flags.eject_pending = 1;
 				kobject_uevent(&device->dev.kobj, KOBJ_OFFLINE);
-				return;
+				goto out;
 			}
 			break;
 		}
@@ -130,18 +132,20 @@ static void container_notify_cb(acpi_handle handle, u32 type, void *context)
 		if (!acpi_bus_get_device(handle, &device) && device) {
 			device->flags.eject_pending = 1;
 			kobject_uevent(&device->dev.kobj, KOBJ_OFFLINE);
-			return;
+			goto out;
 		}
 		break;
 
 	default:
 		/* non-hotplug event; possibly handled by other handler */
-		return;
+		goto out;
 	}
 
 	/* Inform firmware that the hotplug operation has completed */
 	(void) acpi_evaluate_hotplug_ost(handle, type, ost_code, NULL);
-	return;
+
+ out:
+	acpi_scan_lock_release();
 }
 
 static bool is_container(acpi_handle handle)
diff --git a/drivers/acpi/dock.c b/drivers/acpi/dock.c
index 68d720a..4fdea38 100644
--- a/drivers/acpi/dock.c
+++ b/drivers/acpi/dock.c
@@ -744,7 +744,9 @@ static void acpi_dock_deferred_cb(void *context)
 {
 	struct dock_data *data = context;
 
+	acpi_scan_lock_acquire();
 	dock_notify(data->handle, data->event, data->ds);
+	acpi_scan_lock_release();
 	kfree(data);
 }
 
@@ -757,20 +759,31 @@ static int acpi_dock_notifier_call(struct notifier_block *this,
 	if (event != ACPI_NOTIFY_BUS_CHECK && event != ACPI_NOTIFY_DEVICE_CHECK
 	   && event != ACPI_NOTIFY_EJECT_REQUEST)
 		return 0;
+
+	acpi_scan_lock_acquire();
+
 	list_for_each_entry(dock_station, &dock_stations, sibling) {
 		if (dock_station->handle == handle) {
 			struct dock_data *dd;
+			acpi_status status;
 
 			dd = kmalloc(sizeof(*dd), GFP_KERNEL);
 			if (!dd)
-				return 0;
+				break;
+
 			dd->handle = handle;
 			dd->event = event;
 			dd->ds = dock_station;
-			acpi_os_hotplug_execute(acpi_dock_deferred_cb, dd);
-			return 0 ;
+			status = acpi_os_hotplug_execute(acpi_dock_deferred_cb,
+							 dd);
+			if (ACPI_FAILURE(status))
+				kfree(dd);
+
+			break;
 		}
 	}
+
+	acpi_scan_lock_release();
 	return 0;
 }
 
diff --git a/drivers/acpi/processor_driver.c b/drivers/acpi/processor_driver.c
index c5d2fd8..cbf1f12 100644
--- a/drivers/acpi/processor_driver.c
+++ b/drivers/acpi/processor_driver.c
@@ -683,8 +683,11 @@ static void acpi_processor_hotplug_notify(acpi_handle handle,
 	struct acpi_device *device = NULL;
 	struct acpi_eject_event *ej_event = NULL;
 	u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE; /* default */
+	acpi_status status;
 	int result;
 
+	acpi_scan_lock_acquire();
+
 	switch (event) {
 	case ACPI_NOTIFY_BUS_CHECK:
 	case ACPI_NOTIFY_DEVICE_CHECK:
@@ -733,25 +736,32 @@ static void acpi_processor_hotplug_notify(acpi_handle handle,
 			break;
 		}
 
+		get_device(&device->dev);
 		ej_event->device = device;
 		ej_event->event = ACPI_NOTIFY_EJECT_REQUEST;
-		acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
-					(void *)ej_event);
-
-		/* eject is performed asynchronously */
-		return;
+		/* The eject is carried out asynchronously. */
+		status = acpi_os_hotplug_execute(acpi_bus_hot_remove_device,
+						 ej_event);
+		if (ACPI_FAILURE(status)) {
+			put_device(&device->dev);
+			kfree(ej_event);
+			break;
+		}
+		goto out;
 
 	default:
 		ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 				  "Unsupported event [0x%x]\n", event));
 
 		/* non-hotplug event; possibly handled by other handler */
-		return;
+		goto out;
 	}
 
 	/* Inform firmware that the hotplug operation has completed */
 	(void) acpi_evaluate_hotplug_ost(handle, event, ost_code, NULL);
-	return;
+
+ out:
+	acpi_scan_lock_release();
 }
 
 static acpi_status is_processor_device(acpi_handle handle)
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index c7676ee..d16a94e 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -42,6 +42,18 @@ struct acpi_device_bus_id{
 	struct list_head node;
 };
 
+void acpi_scan_lock_acquire(void)
+{
+	mutex_lock(&acpi_scan_lock);
+}
+EXPORT_SYMBOL_GPL(acpi_scan_lock_acquire);
+
+void acpi_scan_lock_release(void)
+{
+	mutex_unlock(&acpi_scan_lock);
+}
+EXPORT_SYMBOL_GPL(acpi_scan_lock_release);
+
 int acpi_scan_add_handler(struct acpi_scan_handler *handler)
 {
 	if (!handler || !handler->attach)
@@ -95,8 +107,6 @@ acpi_device_modalias_show(struct device *dev, struct device_attribute *attr, cha
 }
 static DEVICE_ATTR(modalias, 0444, acpi_device_modalias_show, NULL);
 
-static void __acpi_bus_trim(struct acpi_device *start);
-
 /**
  * acpi_bus_hot_remove_device: hot-remove a device and its children
  * @context: struct acpi_eject_event pointer (freed in this func)
@@ -107,7 +117,7 @@ static void __acpi_bus_trim(struct acpi_device *start);
  */
 void acpi_bus_hot_remove_device(void *context)
 {
-	struct acpi_eject_event *ej_event = (struct acpi_eject_event *) context;
+	struct acpi_eject_event *ej_event = context;
 	struct acpi_device *device = ej_event->device;
 	acpi_handle handle = device->handle;
 	acpi_handle temp;
@@ -118,11 +128,19 @@ void acpi_bus_hot_remove_device(void *context)
 
 	mutex_lock(&acpi_scan_lock);
 
+	/* If there is no handle, the device node has been unregistered. */
+	if (!device->handle) {
+		dev_dbg(&device->dev, "ACPI handle missing\n");
+		put_device(&device->dev);
+		goto out;
+	}
+
 	ACPI_DEBUG_PRINT((ACPI_DB_INFO,
 		"Hot-removing device %s...\n", dev_name(&device->dev)));
 
-	__acpi_bus_trim(device);
-	/* Device node has been released. */
+	acpi_bus_trim(device);
+	/* Device node has been unregistered. */
+	put_device(&device->dev);
 	device = NULL;
 
 	if (ACPI_SUCCESS(acpi_get_handle(handle, "_LCK", &temp))) {
@@ -151,6 +169,7 @@ void acpi_bus_hot_remove_device(void *context)
 					  ost_code, NULL);
 	}
 
+ out:
 	mutex_unlock(&acpi_scan_lock);
 	kfree(context);
 	return;
@@ -212,6 +231,7 @@ acpi_eject_store(struct device *d, struct device_attribute *attr,
 		goto err;
 	}
 
+	get_device(&acpi_device->dev);
 	ej_event->device = acpi_device;
 	if (acpi_device->flags.eject_pending) {
 		/* event originated from ACPI eject notification */
@@ -224,7 +244,11 @@ acpi_eject_store(struct device *d, struct device_attribute *attr,
 			ej_event->event, ACPI_OST_SC_EJECT_IN_PROGRESS, NULL);
 	}
 
-	acpi_os_hotplug_execute(acpi_bus_hot_remove_device, (void *)ej_event);
+	status = acpi_os_hotplug_execute(acpi_bus_hot_remove_device, ej_event);
+	if (ACPI_FAILURE(status)) {
+		put_device(&acpi_device->dev);
+		kfree(ej_event);
+	}
 err:
 	return ret;
 }
@@ -779,6 +803,7 @@ static void acpi_device_unregister(struct acpi_device *device)
 	 * no more references.
 	 */
 	acpi_device_set_power(device, ACPI_STATE_D3_COLD);
+	device->handle = NULL;
 	put_device(&device->dev);
 }
 
@@ -1623,14 +1648,14 @@ static acpi_status acpi_bus_device_attach(acpi_handle handle, u32 lvl_not_used,
  * there has been a real error.  There just have been no suitable ACPI objects
  * in the table trunk from which the kernel could create a device and add an
  * appropriate driver.
+ *
+ * Must be called under acpi_scan_lock.
  */
 int acpi_bus_scan(acpi_handle handle)
 {
 	void *device = NULL;
 	int error = 0;
 
-	mutex_lock(&acpi_scan_lock);
-
 	if (ACPI_SUCCESS(acpi_bus_check_add(handle, 0, NULL, &device)))
 		acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,
 				    acpi_bus_check_add, NULL, NULL, &device);
@@ -1641,7 +1666,6 @@ int acpi_bus_scan(acpi_handle handle)
 		acpi_walk_namespace(ACPI_TYPE_ANY, handle, ACPI_UINT32_MAX,
 				    acpi_bus_device_attach, NULL, NULL, NULL);
 
-	mutex_unlock(&acpi_scan_lock);
 	return error;
 }
 EXPORT_SYMBOL(acpi_bus_scan);
@@ -1678,7 +1702,13 @@ static acpi_status acpi_bus_remove(acpi_handle handle, u32 lvl_not_used,
 	return AE_OK;
 }
 
-static void __acpi_bus_trim(struct acpi_device *start)
+/**
+ * acpi_bus_trim - Remove ACPI device node and all of its descendants
+ * @start: Root of the ACPI device nodes subtree to remove.
+ *
+ * Must be called under acpi_scan_lock.
+ */
+void acpi_bus_trim(struct acpi_device *start)
 {
 	/*
 	 * Execute acpi_bus_device_detach() as a post-order callback to detach
@@ -1695,13 +1725,6 @@ static void __acpi_bus_trim(struct acpi_device *start)
 			    acpi_bus_remove, NULL, NULL);
 	acpi_bus_remove(start->handle, 0, NULL, NULL);
 }
-
-void acpi_bus_trim(struct acpi_device *start)
-{
-	mutex_lock(&acpi_scan_lock);
-	__acpi_bus_trim(start);
-	mutex_unlock(&acpi_scan_lock);
-}
 EXPORT_SYMBOL_GPL(acpi_bus_trim);
 
 static int acpi_bus_scan_fixed(void)
@@ -1758,23 +1781,27 @@ int __init acpi_scan_init(void)
 	acpi_csrt_init();
 	acpi_container_init();
 
+	mutex_lock(&acpi_scan_lock);
 	/*
 	 * Enumerate devices in the ACPI namespace.
 	 */
 	result = acpi_bus_scan(ACPI_ROOT_OBJECT);
 	if (result)
-		return result;
+		goto out;
 
 	result = acpi_bus_get_device(ACPI_ROOT_OBJECT, &acpi_root);
 	if (result)
-		return result;
+		goto out;
 
 	result = acpi_bus_scan_fixed();
 	if (result) {
 		acpi_device_unregister(acpi_root);
-		return result;
+		goto out;
 	}
 
 	acpi_update_all_gpes();
-	return 0;
+
+ out:
+	mutex_unlock(&acpi_scan_lock);
+	return result;
 }