packaging(systemd): add cgroup to RestrictNamespaces (closes #163)#184
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…oken Closes #163. Thanks to @mrvellang for catching the latent trap. RestrictNamespaces is an allowlist — anything not enumerated returns EPERM on unshare/clone. Two changes: 1. Add `cgroup` to the allowlist. Without it, the moment we wire up per-child cgroup-v2 namespaces (the natural next step for fork-out isolation), `unshare(CLONE_NEWCGROUP)` silently returns EPERM. As #163 notes, the kind of trap that costs an afternoon to debug. 2. Inline-comment each token (net / mnt / user / pid / cgroup) so a future well-intentioned hardening pass doesn't quietly remove one without noticing what it gates.
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Closes #163. Thanks @mrvellang for catching the latent trap.
`RestrictNamespaces` is an allowlist — anything not enumerated returns `EPERM` on `unshare`/`clone`. Two changes to `packaging/systemd/forkd-controller.service`:
Add `cgroup` to the allowlist. Without it, the moment we wire up per-child cgroup-v2 namespaces (the natural next step for fork-out isolation, and one we're sketching for v0.4 — see `DESIGN-v0.4-USER-API.md`), `unshare(CLONE_NEWCGROUP)` silently returns `EPERM` from inside the service. The kind of trap that costs an afternoon to debug, exactly as systemd unit:
RestrictNamespaces=net mnt user pidblockscgroupnamespace #163 warned.Inline-comment each token (net / mnt / user / pid / cgroup) explaining why it's there. The previous one-line directive made each token equally easy to remove on a future hardening pass; now a reviewer can see what gates what.
No behaviour change today — the controller doesn't yet `unshare(CLONE_NEWCGROUP)`. This unblocks future per-child cgroup namespacing without surfacing the EPERM at the worst moment.