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Subject: Re: [RFC][PATCH v2 06/12] diglim: Interfaces - digest_list_add,
 digest_list_del
From:   Mimi Zohar <zohar@linux.ibm.com>
To:     Roberto Sassu <roberto.sassu@huawei.com>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "mchehab+huawei@kernel.org" <mchehab+huawei@kernel.org>
Cc:     "linux-integrity@vger.kernel.org" <linux-integrity@vger.kernel.org>,
        "linux-security-module@vger.kernel.org" 
        <linux-security-module@vger.kernel.org>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        "linux-kselftest@vger.kernel.org" <linux-kselftest@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Igor Stoppa <igor.stoppa@huawei.com>
Date:   Mon, 02 Aug 2021 11:01:15 -0400
In-Reply-To: <96c7cd3d19254e84a6cb45b2a940e944@huawei.com>
References: <20210726163700.2092768-1-roberto.sassu@huawei.com>
         <20210726163700.2092768-7-roberto.sassu@huawei.com>
         <c9dffd9d29df095660beaa631ff252c4b33629a0.camel@linux.ibm.com>
         <ef7c85dcb096479e95c8c60ccda4d700@huawei.com>
         <1ef95096bee13578b3f906dd9f708c6af9d6ff18.camel@linux.ibm.com>
         <555bf01bee4b4ea7a9bee658366d535a@huawei.com>
         <2c731f07bd08f01f2a3e032814bc65ae9a8494ad.camel@linux.ibm.com>
         <bd0787e0ee4f47baa41abf47976e536c@huawei.com>
         <96c7cd3d19254e84a6cb45b2a940e944@huawei.com>
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On Mon, 2021-08-02 at 08:14 +0000, Roberto Sassu wrote:
> > From: Roberto Sassu [mailto:roberto.sassu@huawei.com]
> > Sent: Friday, July 30, 2021 4:25 PM
> > > From: Mimi Zohar [mailto:zohar@linux.ibm.com]
> > > Sent: Friday, July 30, 2021 4:03 PM
> > > Hi Roberto,
> > >
> > > On Fri, 2021-07-30 at 13:16 +0000, Roberto Sassu wrote:
> > > > > From: Mimi Zohar [mailto:zohar@linux.ibm.com]
> > > > > Sent: Friday, July 30, 2021 2:40 PM
> > >
> > > > > "critical data", in this context, should probably be used for verifying
> > > > > the in memory file digests and other state information haven't been
> > > > > compromised.
> > > >
> > > > Actually, this is what we are doing currently. To keep the
> > > > implementation simple, once the file or the buffer are uploaded
> > > > to the kernel, they will not be modified, just accessed through
> > > > the indexes.
> > >
> > > My main concern about digest lists is their integrity, from loading the
> > > digest lists to their being stored in memory.  A while back, there was
> > > some work on defining a write once memory allocator.  I don't recall
> > > whatever happened to it.  This would be a perfect usecase for that
> > > memory allocator.
> > 
> > Adding Igor in CC.
> > 
> > Regarding loading, everything uploaded to the kernel is carefully
> > evaluated. This should not be a concern. Regarding making them
> > read-only, probably if you can subvert digest lists you can also
> > remove the read-only protection (unless you use an hypervisor).
> 
> I briefly talked with Igor. He also agreed with that, and added that
> it could make it more difficult for an attacker to also disable the
> protection. However, he is not planning to submit an update soon,
> so I wouldn't consider this an option for now.

Hi Roberto, Greg,

As long as others understand and agree to the risk, the IMA details can
be worked out.

thanks,

Mimi