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Subject: Re: [PATCH v10 11/27] ima: Move ima_lsm_policy_notifier into
 ima_namespace
From:   Mimi Zohar <zohar@linux.ibm.com>
To:     Stefan Berger <stefanb@linux.ibm.com>,
        linux-integrity@vger.kernel.org
Cc:     serge@hallyn.com, christian.brauner@ubuntu.com,
        containers@lists.linux.dev, dmitry.kasatkin@gmail.com,
        ebiederm@xmission.com, krzysztof.struczynski@huawei.com,
        roberto.sassu@huawei.com, mpeters@redhat.com, lhinds@redhat.com,
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        jamjoom@us.ibm.com, linux-kernel@vger.kernel.org,
        paul@paul-moore.com, rgb@redhat.com,
        linux-security-module@vger.kernel.org, jmorris@namei.org
Date:   Thu, 17 Feb 2022 16:24:18 -0500
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On Thu, 2022-02-17 at 15:59 -0500, Stefan Berger wrote:
> >
> >> Move the ima_lsm_policy_notifier into the ima_namespace. Each IMA
> >> namespace can now register its own LSM policy change notifier callback.
> >> The policy change notifier for the init_ima_ns still remains in init_ima()
> >> and therefore handle the registration of the callback for all other
> >> namespaces in init_ima_namespace().
> >>
> >> Suppress the kernel warning 'rule for LSM <label> is undefined` for all
> >> other IMA namespaces than the init_ima_ns.
> > Instead of ignoring the warnings totally, perhaps use either the
> > "ratelimited" or "once" function options for non init_ima_ns.  It would
> > be nice if these functions could be namespace aware, so that each
> > affected IMA namespace would contain at least one warning.
> 
> The problem is that any user can now repeatedly create user namespaces 
> and with that IMA namespaces and cause the kernel log to fill up with 
> these messages and also flood the audit log -- I guess one could 
> describe it as an unwanted side-effect. I am afraid that for as long as 
> the kernel log is not namespaced it's probably best to just turn them 
> off for non-init_ima_ns.

There are functions - pr_warn_once() or pr_warn_ratelimited() - that
limit the number of kernel messages.  In addition to the number of
potential kernel messages, there's also the issue of being able to
differentiate between init_ima_ns and other IMA namespaces.  I think
that is more of a concern than rate limiting.

-- 
thanks,

Mimi