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

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Message-Id: <587F7252.4070808@linux.vnet.ibm.com>
Date:   Wed, 18 Jan 2017 19:19:06 +0530
From:   Nayna <nayna@...ux.vnet.ibm.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.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 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@...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'.

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@...ux.intel.com>
>
> /Jarkko
>