linux-kernel - Re: [PATCH v3 0/4] Introduce security_create_user

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Message-ID: <a4db1154-94bc-9833-1665-a88a5eee48de@cloudflare.com>
Date:   Mon, 1 Aug 2022 08:13:57 -0500
From:   Frederick Lawler <fred@...udflare.com>
To:     Paul Moore <paul@...l-moore.com>, Martin KaFai Lau <kafai@...com>
Cc:     kpsingh@...nel.org, revest@...omium.org, jackmanb@...omium.org,
        ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        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,
        ebiederm@...ssion.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
Subject: Re: [PATCH v3 0/4] Introduce security_create_user_ns()

On 7/22/22 7:20 AM, Paul Moore wrote:
> On July 22, 2022 2:12:03 AM Martin KaFai Lau <kafai@...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?

> --
> paul-moore.com
> 
>