Q: Given the following code slice:
```
1 void vmbus_free_ring(struct vmbus_channel *channel)
6 	if (channel->ringbuffer_page) {
7 		__free_pages(channel->ringbuffer_page,```
which has a CWE-401 vulnerability at line:
```
7 		__free_pages(channel->ringbuffer_page,
```
Please analyze the root cause of the vulnerability.