linux-kernel - Re: [PATCH v7 0/7] ima: kexec: measure events between kexec load and execute

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Message-ID: <c99d2151d3c99f86c1e4e2bbf236ad53603e2ff2.camel@linux.ibm.com>
Date: Tue, 18 Feb 2025 14:39:13 -0500
From: Mimi Zohar <zohar@...ux.ibm.com>
To: steven chen <chenste@...ux.microsoft.com>, stefanb@...ux.ibm.com,
        roberto.sassu@...weicloud.com, roberto.sassu@...wei.com,
        eric.snowberg@...cle.com, ebiederm@...ssion.com, paul@...l-moore.com,
        code@...icks.com, bauermann@...abnow.com,
        linux-integrity@...r.kernel.org, kexec@...ts.infradead.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: madvenka@...ux.microsoft.com, nramas@...ux.microsoft.com,
        James.Bottomley@...senPartnership.com, bhe@...hat.com,
        vgoyal@...hat.com, dyoung@...hat.com
Subject: Re: [PATCH v7 0/7] ima: kexec: measure events between kexec load
 and execute

Hi Steven,

I'm ignoring this version of v7.  Please remember to update the version to v8 before re-
posting and update the change log.

thanks,

Mimi

On Tue, 2025-02-18 at 09:20 -0800, steven chen wrote:
> The current kernel behavior is IMA measurements snapshot is taken at
> kexec 'load' and not at kexec 'execute'.  IMA log is then carried
> over to the new kernel after kexec 'execute'.
> 
> New events can be measured during/after the IMA log snapshot at kexec 
> 'load' and before the system boots to the new kernel.  In this scenario,
> the TPM PCRs are extended with these events, but they are not carried
> over to the new kernel after kexec soft reboot since the snapshot is
> already taken.  This results in mismatch between TPM PCR quotes and the
> actual IMA measurements list after kexec soft reboot, which in turn
> results in remote attestation failure.
> 
> To solve this problem - 
>  - allocate the necessary buffer at kexec 'load' time,
>  - populate the buffer with the IMA measurements at kexec 'execute' time, 
>  - and measure two new IMA events 'kexec_load' and 'kexec_execute' as
>    critical data to help detect missing events after kexec soft reboot.


[ ... ]


> Change Log v7:
>  - Incorporated feedback from the community (Stefan Berger, Tyler Hicks) 
>    on v6 of this series[8].
>  - Verified all the patches are bisect-safe by booting into each
>    patch and verifying multiple kexec 'load' operations work,
>    and also verifying kexec soft reboot works, and IMA log gets
>    carried over for each patch.