linux-kernel - Re: [PATCH v5 0/4] Introduce security_create_user

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Date:   Wed, 17 Aug 2022 14:57:40 -0500
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     Paul Moore <paul@...l-moore.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Frederick Lawler <fred@...udflare.com>, kpsingh@...nel.org,
        revest@...omium.org, jackmanb@...omium.org, ast@...nel.org,
        daniel@...earbox.net, andrii@...nel.org, kafai@...com,
        songliubraving@...com, yhs@...com, john.fastabend@...il.com,
        jmorris@...ei.org, serge@...lyn.com,
        stephen.smalley.work@...il.com, eparis@...isplace.org,
        shuah@...nel.org, brauner@...nel.org, casey@...aufler-ca.com,
        bpf@...r.kernel.org, linux-security-module@...r.kernel.org,
        selinux@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        kernel-team@...udflare.com, cgzones@...glemail.com,
        karl@...badwolfsecurity.com, tixxdz@...il.com
Subject: Re: [PATCH v5 0/4] Introduce security_create_user_ns()

Paul Moore <paul@...l-moore.com> writes:

> At the end of the v4 patchset I suggested merging this into lsm/next
> so it could get a full -rc cycle in linux-next, assuming no issues
> were uncovered during testing

What in the world can be uncovered in linux-next for code that has no in
tree users.

That is one of my largest problems.  I want to talk about the users and
the use cases and I don't get dialog.  Nor do I get hey look back there
you missed it.

Since you don't want to rehash this.  I will just repeat my conclusion
that the patchset appears to introduce an ineffective defense that will
achieve nothing in the defense of the kernel, and so all it will achieve
a code maintenance burden and to occasionally break legitimate users of
the user namespace.

Further the process is broken.  You are changing the semantics of an
operation with the introduction of a security hook.  That needs a
man-page and discussion on linux-abi.  In general of the scrutiny we
give to new systems and changed system calls.  As this change
fundamentally changes the semantics of creating a user namespace.

Skipping that part of the process is not simply disagree that is being
irresponsible.

Eric