linux-kernel - Re: [PATCH 2/2] tpm: Add Field Upgrade mode support for Infineon TPM2 modules

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Date:   Sat, 7 May 2022 22:43:48 +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,
        Marten.Lindahl@...s.com, martenli@...s.com, jgg@...pe.ca,
        jsnitsel@...hat.com, nayna@...ux.vnet.ibm.com,
        johannes.holland@...ineon.com, peterhuewe@....de
Subject: Re: [PATCH 2/2] tpm: Add Field Upgrade mode support for Infineon
 TPM2 modules

On Fri, May 06, 2022 at 02:31:48PM +0200, Stefan Mahnke-Hartmann wrote:
> TPM2_GetCapability with a capability that has the property type value
> of TPM_PT_TOTAL_COMMANDS returns a zero length list, when an Infineon
> TPM2 is in Field Upgrade mode.
> Since an Infineon TPM2.0 in Field Upgrade mode returns RC_SUCCESS on
> TPM2_Startup, the Field Upgrade mode has to be detected by
> TPM2_GetCapability.
> 
> Signed-off-by: Stefan Mahnke-Hartmann <stefan.mahnke-hartmann@...ineon.com>
> ---
>  drivers/char/tpm/tpm2-cmd.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index e62a644ce26b..659130e2936e 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -746,6 +746,12 @@ int tpm2_auto_startup(struct tpm_chip *chip)
>  	}
>  
>  	rc = tpm2_get_cc_attrs_tbl(chip);
> +	/*
> +	 * Infineon TPM in Field Upgrade mode will return no data for the number
> +	 * of supported commands.
> +	 */
> +	if (rc == -ENODATA)
> +		rc = TPM2_RC_UPGRADE;

Injecting hardware error codes like this is not considered a great idea.

>  
>  out:
>  	if (rc == TPM2_RC_UPGRADE) {
> -- 
> 2.25.1
> 

BR, Jarkko