Message-ID: <66b377f6-40b4-77da-c02b-2650fa72d0b4@linux.ibm.com>
Date:   Fri, 10 Dec 2021 09:17:14 -0500
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Subject: Re: [PATCH v5 15/16] ima: Move dentries into ima_namespace
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To:     Mimi Zohar <zohar@linux.ibm.com>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        James Bottomley <jejb@linux.ibm.com>
Cc:     linux-integrity@vger.kernel.org, serge@hallyn.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,
        lsturman@redhat.com, puiterwi@redhat.com, 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
References: <20211208221818.1519628-1-stefanb@linux.ibm.com>
 <20211208221818.1519628-16-stefanb@linux.ibm.com>
 <20211209143428.ip6bwry5hqtee5vy@wittgenstein>
 <20211209143749.wk4agkynfqdzftbl@wittgenstein>
 <fb99af21f029b8072435e35731b919f4ec98f89d.camel@linux.ibm.com>
 <e2feaf2f6ac4bc82f328f94ca35d14cdc3ca79d1.camel@linux.ibm.com>
 <20211210114934.tacjnwryihrsx6ln@wittgenstein>
 <2587716d7d021c35e3b6ef22b6e30f44c2b3f98e.camel@linux.ibm.com>
 <6de8d349-74f8-7be4-3854-5c4ac72860ad@linux.ibm.com>
 <d8a6a6827da17825c1aa011256b96d195b1ebf13.camel@linux.ibm.com>
From:   Stefan Berger <stefanb@linux.ibm.com>
In-Reply-To: <d8a6a6827da17825c1aa011256b96d195b1ebf13.camel@linux.ibm.com>
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On 12/10/21 08:02, Mimi Zohar wrote:
> 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.

Ok, I will adjust the Kconfig for this then. This then warrants the 
question whether to move the dentry into the ima_namespace. The current 
code looks like this.

#if !defined(CONFIG_IMA_WRITE_POLICY) && !defined(CONFIG_IMA_READ_POLICY)
         securityfs_remove(ns->policy_dentry);
         ns->policy_dentry = NULL;
         ns->policy_dentry_removed = true;
#elif defined(CONFIG_IMA_WRITE_POLICY)

With IMA_NS selecting IMA_WRITE_POLICY and IMA_READ_POLICY the above 
wouldn't be necessary anymore but I find it 'cleaner' to still have the 
dentry isolated rather than it being a global static as it was before...


>
> thanks,
>
> Mimi
>