linux-kernel - Re: [PATCH v6 2/3] tpm: vtpm_proxy: Implement request

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Date:   Wed, 24 May 2017 19:03:27 -0400
From:   Stefan Berger <stefanb@...ux.vnet.ibm.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     tpmdd-devel@...ts.sourceforge.net,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, jgunthorpe@...idianresearch.com
Subject: Re: [PATCH v6 2/3] tpm: vtpm_proxy: Implement request_locality
 function.

On 05/24/2017 06:21 PM, Jarkko Sakkinen wrote:
> On Wed, May 24, 2017 at 05:39:40PM -0400, Stefan Berger wrote:
>> Implement the request_locality function. To set the locality on the
>> backend we define vendor-specific TPM 1.2 and TPM 2 ordinals and send
>> a command to the backend to set the locality for the next commands.
>>
>> To avoid recursing into requesting the locality, we set the
>> TPM_TRANSMIT_RAW flag when calling tpm_transmit_cmd. To avoid recursing
>> into TPM 2 space related commands, we set the space parameter to NULL.
>>
>> Signed-off-by: Stefan Berger <stefanb@...ux.vnet.ibm.com>
>> ---
>>   drivers/char/tpm/tpm-interface.c  |  1 +
>>   drivers/char/tpm/tpm_vtpm_proxy.c | 36 ++++++++++++++++++++++++++++++++++++
>>   include/uapi/linux/vtpm_proxy.h   |  4 ++++
>>   3 files changed, 41 insertions(+)
>>
>> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
>> index 2eacda2..876d45f 100644
>> --- a/drivers/char/tpm/tpm-interface.c
>> +++ b/drivers/char/tpm/tpm-interface.c
>> @@ -537,6 +537,7 @@ ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct tpm_space *space,
>>   
>>   	return 0;
>>   }
>> +EXPORT_SYMBOL_GPL(tpm_transmit_cmd);
>>   
>>   #define TPM_DIGEST_SIZE 20
>>   #define TPM_RET_CODE_IDX 6
>> diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
>> index 751059d..66024bf 100644
>> --- a/drivers/char/tpm/tpm_vtpm_proxy.c
>> +++ b/drivers/char/tpm/tpm_vtpm_proxy.c
>> @@ -371,6 +371,41 @@ static bool vtpm_proxy_tpm_req_canceled(struct tpm_chip  *chip, u8 status)
>>   	return ret;
>>   }
>>   
>> +static int vtpm_proxy_request_locality(struct tpm_chip *chip, int locality)
>> +{
>> +	struct tpm_buf buf;
>> +	int rc;
>> +	const struct tpm_output_header *header;
>> +
>> +	if (chip->flags & TPM_CHIP_FLAG_TPM2)
>> +		rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS,
>> +				  TPM2_CC_SET_LOCALITY);
> I would always go with this branch.
>
>> +	else
>> +		rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND,
>> +				  TPM_ORD_SET_LOCALITY);
>> +	if (rc)
>> +		return rc;
>> +	tpm_buf_append_u8(&buf, locality);
>> +
>> +	rc = tpm_transmit_cmd(chip, NULL, buf.data, tpm_buf_length(&buf), 0,
>> +			      TPM_TRANSMIT_UNLOCKED | TPM_TRANSMIT_RAW,
>> +			      "attempting to set locality");
>> +	if (rc < 0) {
>> +		locality = rc;
>> +		goto out;
>> +	}
>> +
>> +	header = (const struct tpm_output_header *)buf.data;
>> +	rc = be32_to_cpu(header->return_code);
>> +	if (rc)
>> +		locality = -1;
>> +
>> +out:
>> +	tpm_buf_destroy(&buf);
>> +
>> +	return locality;
>> +}
>> +
>>   static const struct tpm_class_ops vtpm_proxy_tpm_ops = {
>>   	.flags = TPM_OPS_AUTO_STARTUP,
>>   	.recv = vtpm_proxy_tpm_op_recv,
>> @@ -380,6 +415,7 @@ static const struct tpm_class_ops vtpm_proxy_tpm_ops = {
>>   	.req_complete_mask = VTPM_PROXY_REQ_COMPLETE_FLAG,
>>   	.req_complete_val = VTPM_PROXY_REQ_COMPLETE_FLAG,
>>   	.req_canceled = vtpm_proxy_tpm_req_canceled,
>> +	.request_locality = vtpm_proxy_request_locality,
>>   };
>>   
>>   /*
>> diff --git a/include/uapi/linux/vtpm_proxy.h b/include/uapi/linux/vtpm_proxy.h
>> index a69e991..58ac73c 100644
>> --- a/include/uapi/linux/vtpm_proxy.h
>> +++ b/include/uapi/linux/vtpm_proxy.h
>> @@ -46,4 +46,8 @@ struct vtpm_proxy_new_dev {
>>   
>>   #define VTPM_PROXY_IOC_NEW_DEV	_IOWR(0xa1, 0x00, struct vtpm_proxy_new_dev)
>>   
>> +/* vendor specific commands to set locality */
>> +#define TPM2_CC_SET_LOCALITY	0x20001000
>> +#define TPM_ORD_SET_LOCALITY	0x20001000
>> +
>>   #endif /* _UAPI_LINUX_VTPM_PROXY_H */
>> -- 
>> 2.4.3
> What practical benefit you get from these two constants? I understand
> the value range but not so much the redundant code.

If you want to change this, please go ahead and give it a sinle name.
For the code branches above I think that we should at least send a TPM 
1.2 formatted command in case of TPM 1.2 and a TPM 2 formatted one in 
case of TPM 2. It seems just 'proper.'

    Stefan