[pizzalife]

> but the specific module in question in the patch, nf_tables, is not loaded on my Ubuntu 20.04LTS 5.40 kernel running iptables/ufw at least

This doesn't matter since Linux has autoloading of most network modules, and you can cause the modules to be loaded on Ubuntu since it supports unprivileged user/net namespaces.

  ubuntu:~% grep DISTRIB_DESCRIPTION /etc/lsb-release
  DISTRIB_DESCRIPTION="Ubuntu 22.04.2 LTS"
  ubuntu:~% lsmod|grep nf_table
  ubuntu:~% unshare -U -m -n -r
  ubuntu:~% nft add table inet filter
  ubuntu:~% lsmod|grep nf_table
  nf_tables             249856  0

[TacticalCoder]

For comparison, on my Debian Bookworm (aka "testing" but in hard freeze and full freeze in a few days I think, stable release in june) here...

    ...$  lsmod|grep nf_table    (tried without any just to make sure) 
    ...$  unshare -U -m -n -r
    unshare: unshare: failed: Operation not permitted
    ...$  /sbin/nft add table inet filter
    Error: Could not process rule: Operation not permitted
    add table inet filter
    ^^^^^^^^^^^^^^^^^^^^^^

    root #  cat /proc/sys/kernel/unprivileged_userns_clone
    0

[veonik]

Yikes... are other popular distros shipping with unprivileged user namespaces enabled by default?

[marcthe12]

Most, I think Debian has patch to be disabled at runtime via sysctl. The reason is that most containers or sandboxing techniques are root only unless you mix it with user namescapes. So most container or sandbox software use suid(firejail) , root daemon(docker) or user namescapes (podman and flatpak). Looking at the cves, user namespaces is probably the safer option

[galangalalgol]

That is part of enabling rootless containers on rhel or similar.

[waynesonfire]

should have re-written it in rust.

[yjftsjthsd-h]

Rewritten what? The container runtime will need the same access regardless of what it's written in, and rewriting all of Linux (the kernel) would be... ambitious, although it is adopting rust incrementally.

[scns]

The good old Strangler Pattern.

https://martinfowler.com/bliki/StranglerFigApplication.html

[galangalalgol]

Some of the issue though is that a monolithic kernel provides more access than necessary to many things. When they made the locks granular, those might be reasonable boundaries for permissions? At this point I'd rather figure out how to make windows drivers work in redox or something crazy like that.

[failsecure]

Yes and this decision haunts distros like Ubuntu over and over again. There's no easy win though.

[touisteur]

Do you need a user namespace? I'd expect a network namespace to be enough. Am I missing something?

Edit: should've read better, this seems to need CLONE_NEWUSER.

[jwilk]

You need CAP_SYS_ADMIN to create a new network namespace.