linux-kernel - Re: [PATCH v4 1/2] tpm: implement TPM 2.0 capability to get active PCR banks

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Date:   Wed, 18 Jan 2017 15:45:22 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Nayna Jain <nayna@...ux.vnet.ibm.com>
Cc:     tpmdd-devel@...ts.sourceforge.net, peterhuewe@....de,
        tpmdd@...horst.net, jgunthorpe@...idianresearch.com,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] tpm: implement TPM 2.0 capability to get active
 PCR banks

On Wed, Jan 18, 2017 at 03:44:49AM -0500, Nayna Jain wrote:
> This patch implements the TPM 2.0 capability TPM_CAP_PCRS to
> retrieve the active PCR banks from the TPM. This is needed
> to enable extending all active banks as recommended by TPM 2.0
> TCG Specification.
> 
> Signed-off-by: Nayna Jain <nayna@...ux.vnet.ibm.com>
> ---
>  drivers/char/tpm/tpm.h      |  4 ++++
>  drivers/char/tpm/tpm2-cmd.c | 57 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 61 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 1ae9768..dddd573 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -127,6 +127,7 @@ enum tpm2_permanent_handles {
>  };
>  
>  enum tpm2_capabilities {
> +	TPM2_CAP_PCRS		= 5,
>  	TPM2_CAP_TPM_PROPERTIES = 6,
>  };
>  
> @@ -187,6 +188,8 @@ struct tpm_chip {
>  
>  	const struct attribute_group *groups[3];
>  	unsigned int groups_cnt;
> +
> +	u16 active_banks[7];
>  #ifdef CONFIG_ACPI
>  	acpi_handle acpi_dev_handle;
>  	char ppi_version[TPM_PPI_VERSION_LEN + 1];
> @@ -545,4 +548,5 @@ int tpm2_auto_startup(struct tpm_chip *chip);
>  void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type);
>  unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal);
>  int tpm2_probe(struct tpm_chip *chip);
> +ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip);
>  #endif
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index 6eda239..75a7546 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -998,3 +998,60 @@ int tpm2_auto_startup(struct tpm_chip *chip)
>  		rc = -ENODEV;
>  	return rc;
>  }
> +
> +struct tpm2_pcr_selection {
> +	__be16  hash_alg;
> +	u8  size_of_select;
> +	u8  pcr_select[3];
> +} __packed;
> +
> +/**
> + * tpm2_get_pcr_allocation() - get TPM active PCR banks.
> + *
> + * @chip: TPM chip to use.
> + *
> + * Return: Same as with tpm_transmit_cmd.
> + */
> +ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
> +{
> +	struct tpm2_pcr_selection pcr_selection;
> +	struct tpm_buf buf;
> +	void *marker;
> +	unsigned int count = 0;

You shouldn't initialize 'count'.

> +	int rc;
> +	int i;
> +
> +	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
> +	if (rc)
> +		return rc;
> +
> +	tpm_buf_append_u32(&buf, TPM2_CAP_PCRS);
> +	tpm_buf_append_u32(&buf, 0);
> +	tpm_buf_append_u32(&buf, 1);
> +
> +	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, 0,
> +			      "get tpm pcr allocation");
> +	if (rc < 0)
> +		goto out;
> +
> +	count = be32_to_cpup(
> +		(__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
> +
> +	if (count > ARRAY_SIZE(chip->active_banks))
> +		return -ENODEV;
> +
> +	marker = &buf.data[TPM_HEADER_SIZE + 9];
> +	for (i = 0; i < count; i++) {
> +		memcpy(&pcr_selection, marker, sizeof(pcr_selection));
> +		chip->active_banks[i] = be16_to_cpu(pcr_selection.hash_alg);
> +		marker = marker + sizeof(struct tpm2_pcr_selection);
> +	}
> +
> +out:
> +	if (count < ARRAY_SIZE(chip->active_banks))
> +		chip->active_banks[count] = 0;
> +
> +	tpm_buf_destroy(&buf);
> +
> +	return rc;
> +}
> -- 
> 2.5.0

Otherwise,

Reviewed-by: Jarkko Sakkinen <jarkko.sakkien@...ux.intel.com>

/Jarkko