linux-kernel - Re: [PATCH v4 14/14] tpm: Allow locality 2 to be set when initializing the TPM for Secure Launch

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Message-ID: <20210827133011.GJ1200268@ziepe.ca>
Date:   Fri, 27 Aug 2021 10:30:11 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Ross Philipson <ross.philipson@...cle.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        iommu@...ts.linux-foundation.org, linux-integrity@...r.kernel.org,
        linux-doc@...r.kernel.org, dpsmith@...rtussolutions.com,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        luto@...capital.net, kanth.ghatraju@...cle.com,
        trenchboot-devel@...glegroups.com
Subject: Re: [PATCH v4 14/14] tpm: Allow locality 2 to be set when
 initializing the TPM for Secure Launch

On Fri, Aug 27, 2021 at 09:28:37AM -0400, Ross Philipson wrote:
> The Secure Launch MLE environment uses PCRs that are only accessible from
> the DRTM locality 2. By default the TPM drivers always initialize the
> locality to 0. When a Secure Launch is in progress, initialize the
> locality to 2.
> 
> Signed-off-by: Ross Philipson <ross.philipson@...cle.com>
> ---
>  drivers/char/tpm/tpm-chip.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)

Global state like this seems quite dangerous, shouldn't the locality
be selected based on the PCR being accessed, or passed down from
higher up in the call chain?

Jason