ACPI / PM: Walk physical_node_list under physical_node_lock

The list of physical devices corresponding to an ACPI device
object is walked by acpi_system_wakeup_device_seq_show() and
physical_device_enable_wakeup() without taking that object's
physical_node_lock mutex.  Since each of those functions may be
run at any time as a result of a user space action, the lack of
appropriate locking in them may lead to a kernel crash if that
happens during device hot-add or hot-remove involving the device
object in question.

Fix the issue by modifying acpi_system_wakeup_device_seq_show() and
physical_device_enable_wakeup() to use physical_node_lock as
appropriate.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: All <stable@vger.kernel.org>

drivers/acpi/proc.c

@@ -311,6 +311,8 @@ acpi_system_wakeup_device_seq_show(struct seq_file *seq, void *offset)
 			   dev->pnp.bus_id,
 			   (u32) dev->wakeup.sleep_state);
 
+		mutex_lock(&dev->physical_node_lock);
+
 		if (!dev->physical_node_count) {
 			seq_printf(seq, "%c%-8s\n",
 				dev->wakeup.flags.run_wake ? '*' : ' ',
@@ -338,6 +340,8 @@ acpi_system_wakeup_device_seq_show(struct seq_file *seq, void *offset)
 				put_device(ldev);
 			}
 		}
+
+		mutex_unlock(&dev->physical_node_lock);
 	}
 	mutex_unlock(&acpi_device_lock);
 	return 0;
@@ -347,12 +351,16 @@ static void physical_device_enable_wakeup(struct acpi_device *adev)
 {
 	struct acpi_device_physical_node *entry;
 
+	mutex_lock(&adev->physical_node_lock);
+
 	list_for_each_entry(entry,
 		&adev->physical_node_list, node)
 		if (entry->dev && device_can_wakeup(entry->dev)) {
 			bool enable = !device_may_wakeup(entry->dev);
 			device_set_wakeup_enable(entry->dev, enable);
 		}
+
+	mutex_unlock(&adev->physical_node_lock);
 }
 
 static ssize_t