linux-kernel - Re: [PATCH v3] tpm: Add upgrade/reduced mode support for TPM1.2 modules

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Message-ID: <Yp8f+kBQLCKfBrOj@iki.fi>
Date:   Tue, 7 Jun 2022 12:52:58 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Stefan Mahnke-Hartmann <stefan.mahnke-hartmann@...ineon.com>
Cc:     linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        peterhuewe@....de, jgg@...pe.ca
Subject: Re: [PATCH v3] tpm: Add upgrade/reduced mode support for TPM1.2
 modules

On Tue, Jun 07, 2022 at 12:49:11PM +0300, Jarkko Sakkinen wrote:
> On Fri, Jun 03, 2022 at 10:41:58AM +0200, Stefan Mahnke-Hartmann wrote:
> > In case a TPM in failure mode is detected, the TPM should be accessible
> > through a transparent communication channel for analysing purposes (e.g.
> > TPM_GetTestResult) or a field upgrade. Since a TPM in failure mode has
> > similar reduced functionality as in field upgrade mode, the flag
> > TPM_CHIP_FLAG_FIRMWARE_UPGRADE is also valid.
> > 
> > As described in TCG TPM Main Part1 Design Principles, Revision 116,
> > chapter 9.2.1. the TPM also allows an update function in case a TPM is
> > in failure mode.
> > 
> > If the TPM in failure mode is detected, the function tpm1_auto_startup()
> > sets TPM_CHIP_FLAG_FIRMWARE_UPGRADE flag, which is used later during
> > driver initialization/deinitialization to disable functionality which
> > makes no sense or will fail in the current TPM state. The following
> > functionality is affected:
> >  * Do not register TPM as a hwrng
> >  * Do not get pcr allocation
> >  * Do not register sysfs entries which provide information impossible to
> >    obtain in limited mode
> > 
> > Signed-off-by: Stefan Mahnke-Hartmann <stefan.mahnke-hartmann@...ineon.com>
> > ---
> > Changelog:
> >  * v3:
> >    * Change kernel messages
> > 
> >  drivers/char/tpm/tpm.h      | 1 +
> >  drivers/char/tpm/tpm1-cmd.c | 7 ++++++-
> >  2 files changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> > index 2163c6ee0d36..24ee4e1cc452 100644
> > --- a/drivers/char/tpm/tpm.h
> > +++ b/drivers/char/tpm/tpm.h
> > @@ -55,6 +55,7 @@ enum tpm_addr {
> >  #define TPM_WARN_DOING_SELFTEST 0x802
> >  #define TPM_ERR_DEACTIVATED     0x6
> >  #define TPM_ERR_DISABLED        0x7
> > +#define TPM_ERR_FAILEDSELFTEST  0x1C
> >  #define TPM_ERR_INVALID_POSTINIT 38
> >  
> >  #define TPM_TAG_RQU_COMMAND 193
> > diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
> > index f7dc986fa4a0..cf64c7385105 100644
> > --- a/drivers/char/tpm/tpm1-cmd.c
> > +++ b/drivers/char/tpm/tpm1-cmd.c
> > @@ -709,7 +709,12 @@ int tpm1_auto_startup(struct tpm_chip *chip)
> >  	if (rc)
> >  		goto out;
> >  	rc = tpm1_do_selftest(chip);
> > -	if (rc) {
> > +	if (rc == TPM_ERR_FAILEDSELFTEST) {
> > +		dev_warn(&chip->dev, "TPM self test failed, switching to the firmware upgrade mode\n");
> > +		/* A TPM in this state possibly allows or needs a firmware upgrade */
> > +		chip->flags |= TPM_CHIP_FLAG_FIRMWARE_UPGRADE;
> > +		return 0;
> > +	} else if (rc) {
> >  		dev_err(&chip->dev, "TPM self test failed\n");
> >  		goto out;
> >  	}
> > -- 
> > 2.25.1
> > 
> 
> I think this looks good now, thanks for patience:
> 
> Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>

applied

BR, Jarkko