ACPI: video: correct acpi_video_bus_add error processing

acpi_video_bus_get_devices() may fail due to some video output device
doesn't have the _ADR method, and in this case, the error processing
is to simply free the video structure in acpi_video_bus_add(), while
leaving those already registered video output devices in the wild,
which means for some video output device, we have already registered
a backlight interface and installed a notification handler for it.
So it can happen when user is using this system, on hotkey pressing,
the notification handler will send a keycode through a non-existing
input device, causing kernel freeze.

To solve this problem, free all those already registered video output
devices once something goes wrong in acpi_video_bus_get_devices(), so
that no wild backlight interfaces and notification handlers exist.

References: https://bugzilla.kernel.org/show_bug.cgi?id=51731
Reported-and-tested-by: <i-tek@web.de>
Signed-off-by: NAaron Lu <aaron.lu@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/video.c

@@ -167,7 +167,8 @@ struct acpi_video_device_flags {
 	u8 dvi:1;
 	u8 bios:1;
 	u8 unknown:1;
-	u8 reserved:2;
+	u8 notify:1;
+	u8 reserved:1;
 };
 
 struct acpi_video_device_cap {
@@ -1074,12 +1075,11 @@ acpi_video_bus_get_one_device(struct acpi_device *device,
 	struct acpi_video_device *data;
 	struct acpi_video_device_attrib* attribute;
 
-	if (!device || !video)
-		return -EINVAL;
-
 	status =
 	    acpi_evaluate_integer(device->handle, "_ADR", NULL, &device_id);
-	if (ACPI_SUCCESS(status)) {
+	/* Some device omits _ADR, we skip them instead of fail */
+	if (ACPI_FAILURE(status))
+		return 0;
 
 	data = kzalloc(sizeof(struct acpi_video_device), GFP_KERNEL);
 	if (!data)
@@ -1117,8 +1117,7 @@ acpi_video_bus_get_one_device(struct acpi_device *device,
 			data->flags.bios = 1;
 	} else {
 		/* Check for legacy IDs */
-			device_type = acpi_video_get_device_type(video,
-								 device_id);
+		device_type = acpi_video_get_device_type(video, device_id);
 		/* Ignore bits 16 and 18-20 */
 		switch (device_type & 0xffe2ffff) {
 			case ACPI_VIDEO_DISPLAY_LEGACY_MONITOR:
@@ -1138,28 +1137,18 @@ acpi_video_bus_get_one_device(struct acpi_device *device,
 	acpi_video_device_bind(video, data);
 	acpi_video_device_find_cap(data);
 
-		status = acpi_install_notify_handler(device->handle,
-						     ACPI_DEVICE_NOTIFY,
-						     acpi_video_device_notify,
-						     data);
-		if (ACPI_FAILURE(status)) {
-			printk(KERN_ERR PREFIX
-					  "Error installing notify handler\n");
-			if(data->brightness)
-				kfree(data->brightness->levels);
-			kfree(data->brightness);
-			kfree(data);
-			return -ENODEV;
-		}
+	status = acpi_install_notify_handler(device->handle, ACPI_DEVICE_NOTIFY,
+					     acpi_video_device_notify, data);
+	if (ACPI_FAILURE(status))
+		dev_err(&device->dev, "Error installing notify handler\n");
+	else
+		data->flags.notify = 1;
 
 	mutex_lock(&video->device_list_lock);
 	list_add_tail(&data->entry, &video->video_device_list);
 	mutex_unlock(&video->device_list_lock);
 
-		return 0;
-	}
-
-	return -ENOENT;
+	return status;
 }
 
 /*
@@ -1452,9 +1441,8 @@ acpi_video_bus_get_devices(struct acpi_video_bus *video,
 
 		status = acpi_video_bus_get_one_device(dev, video);
 		if (status) {
-			printk(KERN_WARNING PREFIX
-					"Can't attach device\n");
-			continue;
+			dev_err(&dev->dev, "Can't attach device\n");
+			break;
 		}
 	}
 	return status;
@@ -1467,13 +1455,14 @@ static int acpi_video_bus_put_one_device(struct acpi_video_device *device)
 	if (!device || !device->video)
 		return -ENOENT;
 
+	if (device->flags.notify) {
 		status = acpi_remove_notify_handler(device->dev->handle,
-					    ACPI_DEVICE_NOTIFY,
-					    acpi_video_device_notify);
-	if (ACPI_FAILURE(status)) {
-		printk(KERN_WARNING PREFIX
+				ACPI_DEVICE_NOTIFY, acpi_video_device_notify);
+		if (ACPI_FAILURE(status))
+			dev_err(&device->dev->dev,
 					"Can't remove video notify handler\n");
 	}
+
 	if (device->backlight) {
 		backlight_device_unregister(device->backlight);
 		device->backlight = NULL;
@@ -1755,7 +1744,7 @@ static int acpi_video_bus_add(struct acpi_device *device)
 
 	error = acpi_video_bus_get_devices(video, device);
 	if (error)
-		goto err_free_video;
+		goto err_put_video;
 
 	video->input = input = input_allocate_device();
 	if (!input) {