SYSCALL_DEFINE3(sendmsg, int, fd, struct user_msghdr __user *, msg, unsigned int, flags)
{
	if (flags & MSG_CMSG_COMPAT)
		return -EINVAL;
	return __sys_sendmsg(fd, msg, flags);
}

Historically, this outdated classification described vulnerabilities from improper handling of data inputs, leading to unexpected program behavior or errors when input validation fails.