linux-kernel - Re: [PATCH v14 16/19] tpm, tpm_tis: Allow locality to be set to a different value

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Message-ID: <799b6ed6-c23f-44ca-96bb-d4683fc92c33@apertussolutions.com>
Date: Wed, 23 Apr 2025 15:38:35 -0400
From: "Daniel P. Smith" <dpsmith@...rtussolutions.com>
To: Stefano Garzarella <sgarzare@...hat.com>,
 Ross Philipson <ross.philipson@...cle.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
 linux-integrity@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-crypto@...r.kernel.org, kexec@...ts.infradead.org,
 linux-efi@...r.kernel.org, iommu@...ts.linux.dev, tglx@...utronix.de,
 mingo@...hat.com, bp@...en8.de, hpa@...or.com, dave.hansen@...ux.intel.com,
 ardb@...nel.org, mjg59@...f.ucam.org, James.Bottomley@...senpartnership.com,
 peterhuewe@....de, jarkko@...nel.org, jgg@...pe.ca, luto@...capital.net,
 nivedita@...m.mit.edu, herbert@...dor.apana.org.au, davem@...emloft.net,
 corbet@....net, ebiederm@...ssion.com, dwmw2@...radead.org,
 baolu.lu@...ux.intel.com, kanth.ghatraju@...cle.com,
 andrew.cooper3@...rix.com, trenchboot-devel@...glegroups.com
Subject: Re: [PATCH v14 16/19] tpm, tpm_tis: Allow locality to be set to a
 different value

On 4/22/25 06:20, Stefano Garzarella wrote:
> On Mon, Apr 21, 2025 at 09:27:09AM -0700, Ross Philipson wrote:
>> DRTM needs to be able to set the locality used by kernel. Provide
>> a one-shot function tpm_chip_set_locality() for the purpose.
>>
>> Signed-off-by: Ross Philipson <ross.philipson@...cle.com>
>> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
>> ---
>> drivers/char/tpm/tpm-chip.c     | 34 ++++++++++++++++++++++++++++++++-
>> drivers/char/tpm/tpm_tis_core.c |  2 ++
>> include/linux/tpm.h             |  4 ++++
>> 3 files changed, 39 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
>> index e25daf2396d3..a603f0dadd43 100644
>> --- a/drivers/char/tpm/tpm-chip.c
>> +++ b/drivers/char/tpm/tpm-chip.c
>> @@ -44,7 +44,7 @@ static int tpm_request_locality(struct tpm_chip *chip)
>>     if (!chip->ops->request_locality)
>>         return 0;
>>
>> -    rc = chip->ops->request_locality(chip, 0);
>> +    rc = chip->ops->request_locality(chip, chip->kernel_locality);
>>     if (rc < 0)
>>         return rc;
>>
>> @@ -380,6 +380,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
>>     }
>>
>>     chip->locality = -1;
>> +    chip->kernel_locality = 0;
>>     return chip;
>>
>> out:
>> @@ -695,3 +696,34 @@ void tpm_chip_unregister(struct tpm_chip *chip)
>>     tpm_del_char_device(chip);
>> }
>> EXPORT_SYMBOL_GPL(tpm_chip_unregister);
>> +
>> +/**
>> + * tpm_chip_set_locality() - Set the TPM locality kernel uses
>> + * @chip:    &tpm_chip instance
>> + * @locality:   new locality
>> + *
>> + * This a one-shot function. Returns zero or POSIX error on failure.
>> + */
>> +int tpm_chip_set_locality(struct tpm_chip *chip, u8 locality)
>> +{
>> +    int ret;
>> +
>> +    if (locality < 0 || locality >= TPM_MAX_LOCALITY)
> 
> Since `locality` is unsigned, we can skip the `locality < 0` check.

You are correct, will be fixed.

>> +        return -EINVAL;
>> +
>> +    ret = tpm_try_get_ops(chip);
>> +    if (ret)
>> +        return ret;
>> +
>> +    if (!(chip->flags & TPM_CHIP_FLAG_SET_LOCALITY_ENABLED)) {
>> +        tpm_put_ops(chip);
>> +        return -EINVAL;
> 
> IIUC this operation is allowed only one time.
> So, this case seems more like an operation that's not allowed because 
> it's already been done, so what about returning "-EPERM".

Sure we can change it to "-EPERM".


v/r,
Daniel P. Smith

> 
>> +    }
>> +
>> +    chip->kernel_locality = locality;
>> +    chip->flags &= ~TPM_CHIP_FLAG_SET_LOCALITY_ENABLED;
>> +    tpm_put_ops(chip);
>> +
>> +    return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(tpm_chip_set_locality);
>> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/ 
>> tpm_tis_core.c
>> index 222081e5c7f7..2bc0cf46adbf 100644
>> --- a/drivers/char/tpm/tpm_tis_core.c
>> +++ b/drivers/char/tpm/tpm_tis_core.c
>> @@ -1124,6 +1124,8 @@ int tpm_tis_core_init(struct device *dev, struct 
>> tpm_tis_data *priv, int irq,
>>     if (IS_ERR(chip))
>>         return PTR_ERR(chip);
>>
>> +    chip->flags |= TPM_CHIP_FLAG_SET_LOCALITY_ENABLED;
>> +
>> #ifdef CONFIG_ACPI
>>     chip->acpi_dev_handle = acpi_dev_handle;
>> #endif
>> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
>> index 86fe8f6a2d52..884791acba2e 100644
>> --- a/include/linux/tpm.h
>> +++ b/include/linux/tpm.h
>> @@ -207,6 +207,8 @@ struct tpm_chip {
>>
>>     /* active locality */
>>     int locality;
>> +    /* the locality used by kernel */
>> +    u8 kernel_locality;
>>
>> #ifdef CONFIG_TCG_TPM2_HMAC
>>     /* details for communication security via sessions */
>> @@ -355,6 +357,7 @@ enum tpm_chip_flags {
>>     TPM_CHIP_FLAG_SUSPENDED            = BIT(8),
>>     TPM_CHIP_FLAG_HWRNG_DISABLED        = BIT(9),
>>     TPM_CHIP_FLAG_DISABLE            = BIT(10),
>> +    TPM_CHIP_FLAG_SET_LOCALITY_ENABLED    = BIT(11),
>> };
>>
>> #define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)
>> @@ -448,6 +451,7 @@ static inline u32 tpm2_rc_value(u32 rc)
>> extern int tpm_is_tpm2(struct tpm_chip *chip);
>> extern __must_check int tpm_try_get_ops(struct tpm_chip *chip);
>> extern void tpm_put_ops(struct tpm_chip *chip);
>> +int tpm_chip_set_locality(struct tpm_chip *chip, u8 locality);
>> extern ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct tpm_buf 
>> *buf,
>>                 size_t min_rsp_body_length, const char *desc);
>> extern int tpm_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
>> -- 
>> 2.39.3
>>
>>
>