HID: hidraw: improve error handling in hidraw_init()

Several improvements in error handling:
- do not report success if alloc_chrdev_region() failed
- check for error code of cdev_add()
- use unregister_chrdev_region() instead of unregister_chrdev()
  if class_create() failed

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hidraw.c

@@ -559,21 +559,28 @@ int __init hidraw_init(void)
 
 	if (result < 0) {
 		pr_warn("can't get major number\n");
-		result = 0;
 		goto out;
 	}
 
 	hidraw_class = class_create(THIS_MODULE, "hidraw");
 	if (IS_ERR(hidraw_class)) {
 		result = PTR_ERR(hidraw_class);
-		unregister_chrdev(hidraw_major, "hidraw");
-		goto out;
+		goto error_cdev;
 	}
 
         cdev_init(&hidraw_cdev, &hidraw_ops);
-        cdev_add(&hidraw_cdev, dev_id, HIDRAW_MAX_DEVICES);
+	result = cdev_add(&hidraw_cdev, dev_id, HIDRAW_MAX_DEVICES);
+	if (result < 0)
+		goto error_class;
+
 out:
 	return result;
+
+error_class:
+	class_destroy(hidraw_class);
+error_cdev:
+	unregister_chrdev_region(dev_id, HIDRAW_MAX_DEVICES);
+	goto out;
 }
 
 void hidraw_exit(void)