Q: Given the following code slice:
```
1 static int gpio_chrdev_release(struct inode *inode, struct file *file)
3 	struct gpio_chardev_data *cdev = file->private_data;
6 	bitmap_free(cdev->watched_lines);```
which has a CWE-457 vulnerability at line:
```
6 	bitmap_free(cdev->watched_lines);
```
Please analyze the root cause of the vulnerability.