linux-kernel - Re: [PATCH v5 15/16] ima: Move dentries into ima

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Date:   Fri, 10 Dec 2021 08:02:13 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Stefan Berger <stefanb@...ux.ibm.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        James Bottomley <jejb@...ux.ibm.com>
Cc:     linux-integrity@...r.kernel.org, serge@...lyn.com,
        containers@...ts.linux.dev, dmitry.kasatkin@...il.com,
        ebiederm@...ssion.com, krzysztof.struczynski@...wei.com,
        roberto.sassu@...wei.com, mpeters@...hat.com, lhinds@...hat.com,
        lsturman@...hat.com, puiterwi@...hat.com, jamjoom@...ibm.com,
        linux-kernel@...r.kernel.org, paul@...l-moore.com, rgb@...hat.com,
        linux-security-module@...r.kernel.org, jmorris@...ei.org
Subject: Re: [PATCH v5 15/16] ima: Move dentries into ima_namespace

On Fri, 2021-12-10 at 07:40 -0500, Stefan Berger wrote:
> On 12/10/21 07:09, Mimi Zohar wrote:
> > On Fri, 2021-12-10 at 12:49 +0100, Christian Brauner wrote:
> >>> There's still the problem that if you write the policy, making the file
> >>> disappear then unmount and remount securityfs it will come back.  My
> >>> guess for fixing this is that we only stash the policy file reference,
> >>> create it if NULL but then set the pointer to PTR_ERR(-EINVAL) or
> >>> something and refuse to create it for that value.
> >> Some sort of indicator that gets stashed in struct ima_ns that the file
> >> does not get recreated on consecutive mounts. That shouldn't be hard to
> >> fix.
> > The policy file disappearing is for backwards compatibility, prior to
> > being able to extend the custom policy.  For embedded usecases,
> > allowing the policy to be written exactly once might makes sense.  Do
> > we really want/need to continue to support removing the policy in
> > namespaces?
> 
> I don't have an answer but should the behavior for the same #define in 
> this case be different for host and namespaces? Or should we just 
> 'select IMA_WRITE_POLICY and IMA_READ_POLICY' when IMA_NS is selected?

The latter option sounds good.  Being able to analyze the namespace
policy is really important.

thanks,

Mimi