linux-kernel - Re: [PATCH v8 0/4] Carry forward IMA measurement log on kexec on ARM64

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Date:   Tue, 03 Nov 2020 10:18:33 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        bauerman@...ux.ibm.com, robh@...nel.org,
        gregkh@...uxfoundation.org, james.morse@....com,
        catalin.marinas@....com, sashal@...nel.org, will@...nel.org,
        mpe@...erman.id.au, benh@...nel.crashing.org, paulus@...ba.org,
        robh+dt@...nel.org, frowand.list@...il.com,
        vincenzo.frascino@....com, mark.rutland@....com,
        dmitry.kasatkin@...il.com, jmorris@...ei.org, serge@...lyn.com,
        pasha.tatashin@...een.com, allison@...utok.net,
        kstewart@...uxfoundation.org, takahiro.akashi@...aro.org,
        tglx@...utronix.de, masahiroy@...nel.org, bhsharma@...hat.com,
        mbrugger@...e.com, hsinyi@...omium.org, tao.li@...o.com,
        christophe.leroy@....fr
Cc:     linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, prsriva@...ux.microsoft.com,
        balajib@...ux.microsoft.com
Subject: Re: [PATCH v8 0/4] Carry forward IMA measurement log on kexec on
 ARM64

On Fri, 2020-10-30 at 10:44 -0700, Lakshmi Ramasubramanian wrote:
> On kexec file load Integrity Measurement Architecture (IMA) subsystem
> may verify the IMA signature of the kernel and initramfs, and measure
> it. The command line parameters passed to the kernel in the kexec call
> may also be measured by IMA. A remote attestation service can verify
> the measurement through the IMA log and the TPM PCR data. This can be
> achieved only if the IMA measurement log is carried over from
> the current kernel to the next kernel across the kexec call.

Nice, but you might want to tweak it a bit.  This is just a suggestion.
"A remote attestation service can verify a TPM quote based on the TPM
event log, the IMA measurement list, and the TPM PCR data".

> However in the current implementation the IMA measurement logs are not
> carried over on ARM64 platforms. Therefore a remote attestation service
> cannot verify the authenticity of the running kernel on ARM64 platforms
> when the kernel is updated through the kexec system call.

The paragraphs above and below are redundant.  The first paragraph
already explained why carrying the measurement across kexec is needed. 
Perhaps drop the above paragraph.

> This patch series adds support for carrying forward the IMA measurement
> log on kexec on ARM64. powerpc already supports carrying forward
> the IMA measurement log on kexec.

And invert these sentences, starting the paragraph with "Powerpc
already" and ending with ARM64.

> 
> This series refactors the platform independent code defined for powerpc
> such that it can be reused for ARM64 as well. A chosen node namely
> "linux,ima-kexec-buffer" is added to the DTB for ARM64 to hold
> the address and the size of the memory reserved to carry
> the IMA measurement log.

^This patch set moves ..."

Thanks,

Mimi

> 
> This patch series has been tested for ARM64 platform using QEMU.
> I would like help from the community for testing this change on powerpc.
> Thanks.
> 
> This patch series is based on
> commit 598a597636f8 ("Merge tag 'afs-fixes-20201029' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs")
> in https://github.com/torvalds/linux "master" branch.