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From:   KP Singh <kpsingh@kernel.org>
Date:   Tue, 2 Aug 2022 23:24:49 +0200
Message-ID: <CACYkzJ7=Cvo9qncMX_5_Wp1zNNWDyh3DxdOLq_ysWxDCs8VC8g@mail.gmail.com>
Subject: Re: [PATCH v3 0/4] Introduce security_create_user_ns()
To:     Paul Moore <paul@paul-moore.com>
Cc:     Frederick Lawler <fred@cloudflare.com>,
        Martin KaFai Lau <kafai@fb.com>, revest@chromium.org,
        jackmanb@chromium.org, ast@kernel.org, daniel@iogearbox.net,
        andrii@kernel.org, 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,
        ebiederm@xmission.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
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Precedence: bulk

On Mon, Aug 1, 2022 at 5:19 PM Paul Moore <paul@paul-moore.com> wrote:
>
> On Mon, Aug 1, 2022 at 9:13 AM Frederick Lawler <fred@cloudflare.com> wrote:
> > On 7/22/22 7:20 AM, Paul Moore wrote:
> > > On July 22, 2022 2:12:03 AM Martin KaFai Lau <kafai@fb.com> wrote:
> > >
> > >> On Thu, Jul 21, 2022 at 12:28:04PM -0500, Frederick Lawler wrote:
> > >>> While creating a LSM BPF MAC policy to block user namespace creation, we
> > >>> used the LSM cred_prepare hook because that is the closest hook to prevent
> > >>> a call to create_user_ns().
> > >>>
> > >>> The calls look something like this:
> > >>>
> > >>> cred = prepare_creds()
> > >>> security_prepare_creds()
> > >>> call_int_hook(cred_prepare, ...
> > >>> if (cred)
> > >>> create_user_ns(cred)
> > >>>
> > >>> We noticed that error codes were not propagated from this hook and
> > >>> introduced a patch [1] to propagate those errors.
> > >>>
> > >>> The discussion notes that security_prepare_creds()
> > >>> is not appropriate for MAC policies, and instead the hook is
> > >>> meant for LSM authors to prepare credentials for mutation. [2]
> > >>>
> > >>> Ultimately, we concluded that a better course of action is to introduce
> > >>> a new security hook for LSM authors. [3]
> > >>>
> > >>> This patch set first introduces a new security_create_user_ns() function
> > >>> and userns_create LSM hook, then marks the hook as sleepable in BPF.
> > >> Patch 1 and 4 still need review from the lsm/security side.
> > >
> > > This patchset is in my review queue and assuming everything checks out, I expect to merge it after the upcoming merge window closes.
> > >
> > > I would also need an ACK from the BPF LSM folks, but they're CC'd on this patchset.
> >
> > Based on last weeks comments, should I go ahead and put up v4 for
> > 5.20-rc1 when that drops, or do I need to wait for more feedback?
>
> In general it rarely hurts to make another revision, and I think
> you've gotten some decent feedback on this draft, especially around
> the BPF LSM tests; I think rebasing on Linus tree after the upcoming
> io_uring changes are merged would be a good idea.  Although as a
> reminder to the BPF LSM folks - I'm looking at you KP Singh :) - I
> need an ACK from you guys before I merge the BPF related patches

Apologies, I was on vacation. I am looking at the patches now.
Reviews and acks coming soon :)

- KP

> (patches {2,3}/4).  For the record, I think the SELinux portion of
> this patchset (path 4/4) is fine.
>

[...]

>
> --
> paul-moore.com