__nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags)
{
	struct nlmsghdr *nlh;
	int size = nlmsg_msg_size(len);

	nlh = (struct nlmsghdr *)skb_put(skb, NLMSG_ALIGN(size));
	nlh->nlmsg_type = type;
	nlh->nlmsg_len = size;
	nlh->nlmsg_flags = flags;
	nlh->nlmsg_pid = portid;
	nlh->nlmsg_seq = seq;
	if (!__builtin_constant_p(size) || NLMSG_ALIGN(size) - size != 0)
		memset(nlmsg_data(nlh) + len, 0, NLMSG_ALIGN(size) - size);
	return nlh;
}

The product calls free() twice on the same memory address, potentially leading to modification of unexpected memory locations.