Re: [PATCH v2 0/4] Partially sandbox Cloud Hypervisor, crosvm, virtiofsd, and the router

Alyssa Ross
2025-12-02T13:15:13Z

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Demi Marie Obenour <demiobenour@gmail.com> writes:

> This restricts the access of these programs to the system. Seccomp is
> not enabled, though, and the processes still run as root. Full
> sandboxing needs additional work. In particular, Cloud Hypervisor
> should receive access to VFIO devices via file descriptor passing.
>
> Sandboxing Cloud Hypervisor requires the use of sh, as there is no s6
> or execline program to increase hard resource limits.

Yes there is! It's poorly named though — presumably the hard limit
functionality was added later. We now do this in application VMs
for Pipewire:

https://spectrum-os.org/git/spectrum/tree/img/app/image/usr/bin/init?id=decd54105e6a54fee737ea436fcb1642141b337e#n5

> D-Bus and the portal are not sandboxed. They have full access to all
> user files by design, so a breach of either is catastrophic no matter
> what. Furthermore, sandboxing them even slightly proved very
> difficult.
>
> Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>
> ---
> Changes in v2:
> - Sandbox Cloud Hypervisor, virtiofsd, and the router
> - Link to v1: https://spectrum-os.org/lists/archives/spectrum-devel/20251129-sandbox-v1-1-6dab926504d3@gmail.com
>
> ---
> Demi Marie Obenour (4):
> host/rootfs: Sandbox crosvm
> host/rootfs: Sandbox router
> host/rootfs: Sandbox virtiofsd
> host/rootfs: Sandbox Cloud Hypervisor
>
> host/rootfs/default.nix | 4 +--
> .../template/data/service/spectrum-router/run | 19 +++++++++++--
> .../template/data/service/vhost-user-fs/run | 28 ++++++++++++++++--
> .../template/data/service/vhost-user-gpu/run | 24 +++++++++++++++-
> .../image/etc/udev/rules.d/99-spectrum.rules | 3 ++
> host/rootfs/image/usr/bin/run-vmm | 33 +++++++++++++++++++---
> 6 files changed, 98 insertions(+), 13 deletions(-)
> ---
> base-commit: 44f32b7a4b3cfbb4046447318e6753dd0eb71add
> change-id: 20251129-sandbox-5a42a6a41b59
>
> --
> Sincerely,
> Demi Marie Obenour (she/her/hers)

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