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From:   Paul Moore <paul@paul-moore.com>
Date:   Wed, 17 Aug 2022 17:50:59 -0400
Message-ID: <CAHC9VhQnPAsmjmKo-e84XDJ1wmaOFkTKPjjztsOa9Yrq+AeAQA@mail.gmail.com>
Subject: Re: [PATCH v5 0/4] Introduce security_create_user_ns()
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Frederick Lawler <fred@cloudflare.com>, kpsingh@kernel.org,
        revest@chromium.org, jackmanb@chromium.org, ast@kernel.org,
        daniel@iogearbox.net, andrii@kernel.org, kafai@fb.com,
        songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com,
        jmorris@namei.org, serge@hallyn.com,
        stephen.smalley.work@gmail.com, eparis@parisplace.org,
        shuah@kernel.org, brauner@kernel.org, casey@schaufler-ca.com,
        bpf@vger.kernel.org, linux-security-module@vger.kernel.org,
        selinux@vger.kernel.org, linux-kselftest@vger.kernel.org,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        kernel-team@cloudflare.com, cgzones@googlemail.com,
        karl@bigbadwolfsecurity.com, tixxdz@gmail.com
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On Wed, Aug 17, 2022 at 5:24 PM Eric W. Biederman <ebiederm@xmission.com> wrote:
> I object to adding the new system configuration knob.
>
> Especially when I don't see people explaining why such a knob is a good
> idea.  What is userspace going to do with this new feature that makes it
> worth maintaining in the kernel?

From https://lore.kernel.org/all/CAEiveUdPhEPAk7Y0ZXjPsD=Vb5hn453CHzS9aG-tkyRa8bf_eg@mail.gmail.com/

 "We have valid use cases not specifically related to the
  attack surface, but go into the middle from bpf observability
  to enforcement. As we want to track namespace creation, changes,
  nesting and per task creds context depending on the nature of
  the workload."
 -Djalal Harouni

From https://lore.kernel.org/linux-security-module/CALrw=nGT0kcHh4wyBwUF-Q8+v8DgnyEJM55vfmABwfU67EQn=g@mail.gmail.com/

 "[W]e do want to embrace user namespaces in our code and some of
  our workloads already depend on it. Hence we didn't agree to
  Debian's approach of just having a global sysctl. But there is
  "our code" and there is "third party" code, which might not even
  be open source due to various reasons. And while the path exists
  for that code to do something bad - we want to block it."
 -Ignat Korchagin

From https://lore.kernel.org/linux-security-module/CAHC9VhSKmqn5wxF3BZ67Z+-CV7sZzdnO+JODq48rZJ4WAe8ULA@mail.gmail.com/

 "I've heard you talk about bugs being the only reason why people
  would want to ever block user namespaces, but I think we've all
  seen use cases now where it goes beyond that.  However, even if
  it didn't, the need to build high confidence/assurance systems
  where big chunks of functionality can be disabled based on a
  security policy is a very real use case, and this patchset would
  help enable that."
 -Paul Moore (with apologies for self-quoting)

From https://lore.kernel.org/linux-security-module/CAHC9VhRSCXCM51xpOT95G_WVi=UQ44gNV=uvvG23p8wn16uYSA@mail.gmail.com/

 "One of the selling points of the BPF LSM is that it allows for
  various different ways of reporting and logging beyond audit.
  However, even if it was limited to just audit I believe that
  provides some useful justification as auditing fork()/clone()
  isn't quite the same and could be difficult to do at scale in
  some configurations."
 -Paul Moore (my apologies again)

From https://lore.kernel.org/linux-security-module/20220722082159.jgvw7jgds3qwfyqk@wittgenstein/

 "Nice and straightforward."
 -Christian Brauner

-- 
paul-moore.com