/lib/systemd/system/ is in udev 215-17+deb8u7.
This file is owned by root:root, with mode 0o755.
..
/lib/systemd/system/sockets.target.wants/
/lib/systemd/system/sockets.target.wants/systemd-udevd-control.socket
/lib/systemd/system/sockets.target.wants/systemd-udevd-kernel.socket
/lib/systemd/system/sysinit.target.wants/
/lib/systemd/system/sysinit.target.wants/systemd-udev-trigger.service
/lib/systemd/system/sysinit.target.wants/systemd-udevd.service
/lib/systemd/system/sysinit.target.wants/udev-finish.service
/lib/systemd/system/systemd-udev-settle.service
/lib/systemd/system/systemd-udev-trigger.service
/lib/systemd/system/systemd-udevd-control.socket
/lib/systemd/system/systemd-udevd-kernel.socket
/lib/systemd/system/systemd-udevd.service
/lib/systemd/system/udev-finish.service
/lib/systemd/system/udev.service