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Message-ID: <657ade76-98c5-4f93-9716-b471b31d07e2@oracle.com>
Date: Tue, 20 Feb 2024 14:57:59 -0800
From: ross.philipson@...cle.com
To: Jarkko Sakkinen <jarkko@...nel.org>,
Lino Sanfilippo <l.sanfilippo@...bus.com>,
Alexander Steffen <Alexander.Steffen@...ineon.com>,
"Daniel P. Smith" <dpsmith@...rtussolutions.com>,
Jason Gunthorpe <jgg@...pe.ca>, Sasha Levin <sashal@...nel.org>,
linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Kanth Ghatraju <kanth.ghatraju@...cle.com>,
Peter Huewe <peterhuewe@....de>
Subject: Re: [PATCH 1/3] tpm: protect against locality counter underflow
On 2/20/24 2:26 PM, Jarkko Sakkinen wrote:
> On Tue Feb 20, 2024 at 8:54 PM UTC, Lino Sanfilippo wrote:
>> for (i = 0; i <= MAX_LOCALITY; i++)
>> __tpm_tis_relinquish_locality(priv, i);
>
> I'm pretty unfamiliar with Intel TXT so asking a dummy question:
> if Intel TXT uses locality 2 I suppose we should not try to
> relinquish it, or?
The TPM has five localities (0 - 4). Localities 1 - 4 are for DRTM
support. For TXT, locality 4 is hard wired to the CPU - nothing else can
touch it. Locality 3 is only ever accessible when the CPU is executing
an AC (Authenticated Code) module. That leaves 1 and 2 for the DRTM
software environment to use. If the DRTM software opens 1 or 2, it
should close them before exiting the DRTM.
>
> AFAIK, we don't have a symbol called MAX_LOCALITY.
Daniel added it in the patch set.
Thanks
Ross
>
> BR, Jarkko
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