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Message-ID: <8a4f9cb6cab5ba04eb61e346d0fca16efa4c6703.camel@linux.ibm.com>
Subject: Re: [PATCH v10 26/27] ima: Limit number of policy rules in
 non-init_ima_ns
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,
        lsturman@redhat.com, puiterwi@redhat.com, jejb@linux.ibm.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
Date:   Wed, 23 Feb 2022 12:04:10 -0500
In-Reply-To: <479f09e7-0d39-0281-45ef-5cce4861d24d@linux.ibm.com>
References: <20220201203735.164593-1-stefanb@linux.ibm.com>
         <20220201203735.164593-27-stefanb@linux.ibm.com>
         <5e4a862917785972281bbcb483404da01b71e801.camel@linux.ibm.com>
         <479f09e7-0d39-0281-45ef-5cce4861d24d@linux.ibm.com>
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On Wed, 2022-02-23 at 11:37 -0500, Stefan Berger wrote:
> On 2/23/22 10:38, Mimi Zohar wrote:
> > On Tue, 2022-02-01 at 15:37 -0500, Stefan Berger wrote:
> >> Limit the number of policy rules one can set in non-init_ima_ns to a
> >> hardcoded 1024 rules. If the user attempts to exceed this limit by
> >> setting too many additional rules, emit an audit message with the cause
> >> 'too-many-rules' and simply ignore the newly added rules.
> > This paragraph describes 'what' you're doing, not 'why'.  Please prefix
> > this paragraph with a short, probably one sentence, reason for the
> > change.
> >> Switch the accounting for the memory allocated for IMA policy rules to
> >> GFP_KERNEL_ACCOUNT so that cgroups kernel memory accounting takes effect.
> > Does this change affect the existing IMA policy rules for init_ima_ns?
> 
> There's typically no cgroup for the int_ima_ns, so not effect on 
> init_ima_ns.
> 
> Here's the updated text:
> 
> Limit the number of policy rules one can set in non-init_ima_ns to a
> hardcoded 1024 rules to restrict the amount of memory used for IMA's
> policy.

The question is "why" there should be a difference between the
init_ima_ns and non-init_ima_ns cases.  Perhaps something like, "Only
host root with CAP_SYS_ADMIN may write init_ima_ns policy rules, but in
the non-init_ima_ns case root in the namespace with CAP_MAC_ADMIN
privileges may write IMA policy rules.  Limit the total number of IMA
policy rules per namespace."

>  Ignore the added rules if the user attempts to exceed this
> limit by setting too many additional rules.
> 
> Switch the accounting for the memory allocated for IMA policy rules to
> GFP_KERNEL_ACCOUNT so that cgroups kernel memory accounting takes effect.
> This switch has no effect on the init_ima_ns.

thanks,

Mimi