Re: [PATCH 1/3] tpm: protect against locality counter underflow

From: "Jarkko Sakkinen" <jarkko@kernel.org>
To: "Jarkko Sakkinen" <jarkko@kernel.org>,
	"Lino Sanfilippo" <l.sanfilippo@kunbus.com>,
	"Alexander Steffen" <Alexander.Steffen@infineon.com>,
	"Daniel P. Smith" <dpsmith@apertussolutions.com>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Sasha Levin" <sashal@kernel.org>,
	<linux-integrity@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Cc: "Ross Philipson" <ross.philipson@oracle.com>,
	"Kanth Ghatraju" <kanth.ghatraju@oracle.com>,
	"Peter Huewe" <peterhuewe@gmx.de>
Subject: Re: [PATCH 1/3] tpm: protect against locality counter underflow
Date: Tue, 20 Feb 2024 22:31:23 +0000	[thread overview]
Message-ID: <CZA9GMC718HA.1JFHTTWV563IE@seitikki> (raw)
In-Reply-To: <CZA9CM3PDILC.82JMLUWMB6B7@seitikki>

On Tue Feb 20, 2024 at 10:26 PM UTC, 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?
>
> AFAIK, we don't have a symbol called MAX_LOCALITY.

OK it was called TPM_MAX_LOCALITY :-) I had the patch set applied
in one branch but looked up with wrong symbol name.

So I reformalize my question to two parts:

1. Why does TXT leave locality 2 open in the first place? I did
   not see explanation. Isn't this a bug in TXT?
2. Because localities are not too useful these days given TPM2's
   policy mechanism I cannot recall out of top of my head can
   you have two localities open at same time. So what kind of
   conflict happens when you try to open locality 0 and have
   locality 2 open?

BR, Jarkko