CLSA-2025-1760018787 cloud-init: Fix of CVE-2024-11584

CVE-2024-11584: fix systemd socket unit permission vulnerability to prevent unprivileged user from triggering hotplug-hook commands...

cloud-init through 25.1.2 includes the systemd socket unit cloud-init-hotplugd.socket with default SocketMode that grants 0666 permissions, making it world-writable. This is used for the "/run/cloud-init/hook-hotplug-cmd" FIFO. An unprivileged user could trigger hotplug-hook commands.

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