Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   "Eric W. Biederman" <ebiederm@xmission.com>
To:     Paul Moore <paul@paul-moore.com>
Cc:     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
References: <20220801180146.1157914-1-fred@cloudflare.com>
        <87les7cq03.fsf@email.froward.int.ebiederm.org>
        <CAHC9VhRpUxyxkPaTz1scGeRm+i4KviQQA7WismOX2q5agzC+DQ@mail.gmail.com>
        <87wnbia7jh.fsf@email.froward.int.ebiederm.org>
        <CAHC9VhS3udhEecVYVvHm=tuqiPGh034-xPqXYtFjBk23+p-Szg@mail.gmail.com>
        <877d3ia65v.fsf@email.froward.int.ebiederm.org>
Date:   Mon, 08 Aug 2022 14:43:41 -0500
In-Reply-To: <877d3ia65v.fsf@email.froward.int.ebiederm.org> (Eric
        W. Biederman's message of "Mon, 08 Aug 2022 14:26:04 -0500")
Message-ID: <87bksu8qs2.fsf@email.froward.int.ebiederm.org>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Subject: Re: [PATCH v4 0/4] Introduce security_create_user_ns()
Precedence: bulk

"Eric W. Biederman" <ebiederm@xmission.com> writes:

> Paul Moore <paul@paul-moore.com> writes:
>
>>> I did provide constructive feedback.  My feedback to his problem
>>> was to address the real problem of bugs in the kernel.
>>
>> We've heard from several people who have use cases which require
>> adding LSM-level access controls and observability to user namespace
>> creation.  This is the problem we are trying to solve here; if you do
>> not like the approach proposed in this patchset please suggest another
>> implementation that allows LSMs visibility into user namespace
>> creation.
>
> Please stop, ignoring my feedback, not detailing what problem or
> problems you are actually trying to be solved, and threatening to merge
> code into files that I maintain that has the express purpose of breaking
> my users.
>
> You just artificially constrained the problems, so that no other
> solution is acceptable.  On that basis alone I am object to this whole
> approach to steam roll over me and my code.

If you want an example of what kind of harm it can cause to introduce a
failure where no failure was before I invite you to look at what
happened with sendmail when setuid was modified to fail, when changing
the user of a process would cause RLIMIT_NPROC to be exceeded.

I am not arguing that what you are proposing is that bad but unexpected
failures cause real problems, and at a minimum that needs a better
response than: "There is at least one user that wants a failure here".

Frankly I would love to see an argument that semantically it ever makes
sense for creating a user namespace to fail.  If that argument has
already been made, my apologies to the person who made as I missed it,
in being sick and tired, and frustrated at being blown off, when
I asked for a proper discuss of the problem at hand.

Eric