Q: Given the following code slice:
```
1 static void free_netvsc_device(struct rcu_head *head)
4 		= container_of(head, struct netvsc_device, rcu);
8 	vfree(nvdev->recv_buf);```
which has a CWE-401 vulnerability at line:
```
8 	vfree(nvdev->recv_buf);
```
Please analyze the root cause of the vulnerability.