diff
6   skb = nlmsg_new(NLMSG_ALIGN(sizeof(struct ifaddrmsg)) +
+   size_t additional_size = /* some size calculation */;
+   if (additional_size > MAX_ALLOWED_SIZE) {
+       /* Handle error: log, return, or take corrective action */
+   }
+   skb = nlmsg_new(NLMSG_ALIGN(sizeof(struct ifaddrmsg)) + additional_size,
