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

[Nayna]

On 01/18/2017 07:15 PM, Jarkko Sakkinen wrote:
> 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@xxxxxxxxxxxxxxxxxx>
> > ---
> >   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'.

It is initialized for reason below:

> > +	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;

if  tpm_transmit_cmd()fails, it jumps to out:
where count is used in if(..).

Thanks & Regards,
   - Nayna

> > +
> > +	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@xxxxxxxxxxxxxxx>
>
> /Jarkko