Q: Given the following code slice:
```
1 static int remove_device_files(struct super_block *sb,
2 			       struct qib_devdata *dd)
4 	struct dentry *dir;
5 	char unit[10];
7 	snprintf(unit, sizeof(unit), "%u", dd->unit);
8 	dir = lookup_one_len_unlocked(unit, sb->s_root, strlen(unit));
10 	if (IS_ERR(dir)) {
14 	simple_recursive_removal(dir, NULL);```
which has a CWE-476 vulnerability at line:
```
14 	simple_recursive_removal(dir, NULL);
```
Please analyze the root cause of the vulnerability.