Q: Given the following code slice:
```
1 static ssize_t crw_inject_write(struct file *file, const char __user *buf,
2 				size_t lbuf, loff_t *ppos)
6 	char *buffer;
9 	if (!static_branch_likely(&cio_inject_enabled)) {
14 	buffer = vmemdup_user(buf, lbuf);```
which has a CWE-125 vulnerability at line:
```
14 	buffer = vmemdup_user(buf, lbuf);
```
Please analyze the root cause of the vulnerability.