@lanodan I assume OpenRC doesn't authenticate the pid that connects to the notification socket, which isn't a problem in practice. If OpenRC wanted to fully harden against evil services notifying readiness for other services, its supervisor would need to add a whole layer of complexity for that.

But even then, I don't think it would need a synchronization mechanism, because who cares if the notifier is still around, as long as the main pid is?

s6's new s6-notify-fd-from-socket binary, doing the systemd-to-s6 protocol conversion, mitigates the problem by only using autobind with abstract sockets, so any foreign would-be notifier would need to guess the abstract socket name.