Mariano Abad
f69648753a
Addresses fufesou's #580 re-review: - The child runs in its own process group and the deadline kills the whole group, so a hung loginctl or a leaked grandchild cannot survive the child or keep the pipes open past the reads. Verified: a deliberately leaked sleep grandchild no longer outlives the probe. - The probe parses compositor-controlled data, so before touching the socket the child drops to the runtime directory's owner and refuses to probe at all if the drop fails, rather than parsing untrusted bytes as root. loginctl still runs as root first, since finding the seat needs it. - first_buffered_line now distinguishes an inspected-but-empty pipe (WouldBlock) from an uninspectable one (fcntl or read error): only a real absence of the handshake latches the binary unsupported, an inspection failure does not. - rustfmt-clean.