Q: Given the following code slice:
```
1 struct sk_buff *skb_copy_expand(const struct sk_buff *skb,
2 				int newheadroom, int newtailroom,
3 				gfp_t gfp_mask)
8 	struct sk_buff *n = __alloc_skb(newheadroom + skb->len + newtailroom,```
which has a CWE-787 vulnerability at line:
```
8 	struct sk_buff *n = __alloc_skb(newheadroom + skb->len + newtailroom,
```
Please analyze the root cause of the vulnerability.