linux-kernel - Re: [PATCH] tpm: Detach page allocation from tpm

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Message-ID: <20190926131227.GA6582@linux.intel.com>
Date:   Thu, 26 Sep 2019 16:12:27 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     linux-integrity@...r.kernel.org
Cc:     Mimi Zohar <zohar@...ux.ibm.com>,
        Jerry Snitselaar <jsnitsel@...hat.com>,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        Sumit Garg <sumit.garg@...aro.org>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tpm: Detach page allocation from tpm_buf

On Thu, Sep 26, 2019 at 03:46:35PM +0300, Jarkko Sakkinen wrote:
> On Wed, Sep 25, 2019 at 04:48:41PM +0300, Jarkko Sakkinen wrote:
> > -		tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_RANDOM);
> > +		tpm_buf_reset(&buf, data_ptr, PAGE_SIZE,
> > +			      TPM2_ST_NO_SESSIONS, TPM2_CC_PCR_EXTEND);
> 
> Oops.

Maybe we could use random as the probe for TPM version since we anyway
send a TPM command as a probe for TPM version:

1. Try TPM2 get random.
2. If fail, try TPM1 get random.
3. Output random number to klog.

Something like 8 bytes would be sufficient. This would make sure that
no new change breaks tpm_get_random() and also this would give some
feedback that TPM is at least somewhat working.

/Jarkko