Q: Given the following code slice:
```
1 static int gpio_chrdev_release(struct inode *inode, struct file *file)
2 {
3 	struct gpio_chardev_data *cdev = file->private_data;
4 	struct gpio_device *gdev = cdev->gdev;
5 
6 	bitmap_free(cdev->watched_lines);
7 	blocking_notifier_chain_unregister(&gdev->device_notifier,
8 					   &cdev->device_unregistered_nb);
9 	blocking_notifier_chain_unregister(&gdev->line_state_notifier,
10 					   &cdev->lineinfo_changed_nb);
11 	gpio_device_put(gdev);
12 	kfree(cdev);
13 
14 	return 0;
15 }
```
which has a vulnerability among CWE-457,CWE-476 and among lines:
```
6 	bitmap_free(cdev->watched_lines);
7 	blocking_notifier_chain_unregister(&gdev->device_notifier,
9 	blocking_notifier_chain_unregister(&gdev->line_state_notifier,
12 	kfree(cdev);
```
Please generate five possible patches for the vulnerability.