SYSCALL_DEFINE3(recvmsg, int, fd, struct user_msghdr __user *, msg,
		unsigned int, flags)
{
	if (flags & MSG_CMSG_COMPAT)
		return -EINVAL;
	return __sys_recvmsg(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Historically, this outdated classification described vulnerabilities from improper handling of data inputs, leading to unexpected program behavior or errors when input validation fails.