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Date: Tue, 21 Dec 2021 10:35:15 +0200
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Axel Jonsson <axelj@...s.com>
Cc: axel.jonsson@...s.com, borysmn@...s.com, jgg@...pe.ca,
kernel@...s.com, linux-integrity@...r.kernel.org,
linux-kernel@...r.kernel.org, peterhuewe@....de,
sergio.ruiz@...s.com
Subject: Re: [PATCH v8] tpm: Add Upgrade/Reduced mode support for TPM2 modules
On Mon, Dec 13, 2021 at 08:09:25AM +0100, Axel Jonsson wrote:
> From: axelj <axelj@...s.com>
>
> If something went wrong during the TPM firmware upgrade, like power
> failure or the firmware image file get corrupted, the TPM might end
> up in Upgrade or Failure mode upon the next start. The state is
> persistent between the TPM power cycle/restart.
>
> According to TPM specification:
> * If the TPM is in Upgrade mode, it will answer with TPM2_RC_UPGRADE
> to all commands except TPM2_FieldUpgradeData(). It may also accept
> other commands if it is able to complete them using the previously
> installed firmware.
> * If the TPM is in Failure mode, it will allow performing TPM
> initialization but will not provide any crypto operations.
> Will happily respond to Field Upgrade calls.
>
> Change the behavior of the tpm2_auto_startup(), so it detects the active
> running mode of the TPM by adding the following checks. If
> tpm2_do_selftest() call returns TPM2_RC_UPGRADE, the TPM is in Upgrade
> mode.
> If the TPM is in Failure mode, it will successfully respond to both
> tpm2_do_selftest() and tpm2_startup() calls. Although, will fail to
> answer to tpm2_get_cc_attrs_tbl(). Use this fact to conclude that TPM is
> in Failure mode.
>
> If detected that the TPM is in the Upgrade or Failure mode, the function
> sets TPM_CHIP_FLAG_FIRMWARE_UPGRADE_MODE flag.
>
> The TPM_CHIP_FLAG_FIRMWARE_UPGRADE_MODE flag is used later during driver
> initialization/deinitialization to disable functionality which makes no
> sense or will fail in the current TPM state. Following functionality is
> affected:
> * Do not register TPM as a hwrng
> * Do not register sysfs entries which provide information impossible to
> obtain in limited mode
> * Do not register resource managed character device
>
> Signed-off-by: axelj <axelj@...s.com>
> ---
>
> Notes:
> v2:
> * Commit message updated.
>
> v3:
> * Commit message reworked.
>
> v4:
> * Description of how tpm2_auto_startup() detects the mode added to
> commit message.
>
> v5:
> * Introduce global flag: TPM_CHIP_FLAG_LIMITED_MODE.
> * Add checks for the flag in places that will not work properly when TPM
> functionality is limited.
> * Avoid registering sysfs and character device entries that have no useful
> function in limited mode.
> * Do not register TPM as a hwrng.
> * Do not try to obtain any crypto-related properties from TPM as it will fail
> in limited mode.
>
> v6:
> * Rename the TPM_CHIP_FLAG_LIMITED_MODE to TPM_CHIP_FLAG_FIRMWARE_UPGRADE_MODE
> to reduce confusion. Update info messages.
>
> v7:
> * Clarified in commit message which command can be run in firmware upgrade
> mode
> * Corrected info and style in commit message
> * Renamed TPM_CHIP_FLAG_FIRMWARE_UPGRADE_MODE to TPM_CHIP_FLAG_FIRMWARE_MODE
> * Replaced TPM_CHIP_FLAG_FIRMWARE_MODE flag check with function from
> include/linux/tpm.h
>
> v8:
> * Fixed line formating.
> * Renamed TPM_CHIP_FLAG_FIRMWARE_MODE to TPM_CHIP_FLAG_FIRMWARE_UPGRADE.
>
> drivers/char/tpm/tpm-chip.c | 19 ++++++++++++-------
> drivers/char/tpm/tpm-sysfs.c | 3 +++
> drivers/char/tpm/tpm2-cmd.c | 6 ++++++
> include/linux/tpm.h | 10 ++++++++++
> 4 files changed, 31 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index ddaeceb7e109..b4ed3ae67a4b 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -444,7 +444,7 @@ static int tpm_add_char_device(struct tpm_chip *chip)
> return rc;
> }
>
> - if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> + if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip)) {
> rc = cdev_device_add(&chip->cdevs, &chip->devs);
> if (rc) {
> dev_err(&chip->devs,
> @@ -488,7 +488,8 @@ static void tpm_del_legacy_sysfs(struct tpm_chip *chip)
> {
> struct attribute **i;
>
> - if (chip->flags & (TPM_CHIP_FLAG_TPM2 | TPM_CHIP_FLAG_VIRTUAL))
> + if (chip->flags & (TPM_CHIP_FLAG_TPM2 | TPM_CHIP_FLAG_VIRTUAL) ||
> + tpm_is_firmware_upgrade(chip))
> return;
>
> sysfs_remove_link(&chip->dev.parent->kobj, "ppi");
> @@ -506,7 +507,8 @@ static int tpm_add_legacy_sysfs(struct tpm_chip *chip)
> struct attribute **i;
> int rc;
>
> - if (chip->flags & (TPM_CHIP_FLAG_TPM2 | TPM_CHIP_FLAG_VIRTUAL))
> + if (chip->flags & (TPM_CHIP_FLAG_TPM2 | TPM_CHIP_FLAG_VIRTUAL) ||
> + tpm_is_firmware_upgrade(chip))
> return 0;
>
> rc = compat_only_sysfs_link_entry_to_kobj(
> @@ -536,7 +538,7 @@ static int tpm_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
>
> static int tpm_add_hwrng(struct tpm_chip *chip)
> {
> - if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM))
> + if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM) || tpm_is_firmware_upgrade(chip))
> return 0;
>
> snprintf(chip->hwrng_name, sizeof(chip->hwrng_name),
> @@ -550,6 +552,9 @@ static int tpm_get_pcr_allocation(struct tpm_chip *chip)
> {
> int rc;
>
> + if (tpm_is_firmware_upgrade(chip))
> + return 0;
> +
> rc = (chip->flags & TPM_CHIP_FLAG_TPM2) ?
> tpm2_get_pcr_allocation(chip) :
> tpm1_get_pcr_allocation(chip);
> @@ -612,7 +617,7 @@ int tpm_chip_register(struct tpm_chip *chip)
> return 0;
>
> out_hwrng:
> - if (IS_ENABLED(CONFIG_HW_RANDOM_TPM))
> + if (IS_ENABLED(CONFIG_HW_RANDOM_TPM) && !tpm_is_firmware_upgrade(chip))
> hwrng_unregister(&chip->hwrng);
> out_ppi:
> tpm_bios_log_teardown(chip);
> @@ -637,10 +642,10 @@ EXPORT_SYMBOL_GPL(tpm_chip_register);
> void tpm_chip_unregister(struct tpm_chip *chip)
> {
> tpm_del_legacy_sysfs(chip);
> - if (IS_ENABLED(CONFIG_HW_RANDOM_TPM))
> + if (IS_ENABLED(CONFIG_HW_RANDOM_TPM) && !tpm_is_firmware_upgrade(chip))
> hwrng_unregister(&chip->hwrng);
> tpm_bios_log_teardown(chip);
> - if (chip->flags & TPM_CHIP_FLAG_TPM2)
> + if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip))
> cdev_device_del(&chip->cdevs, &chip->devs);
> tpm_del_char_device(chip);
> }
> diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
> index 63f03cfb8e6a..54c71473aa29 100644
> --- a/drivers/char/tpm/tpm-sysfs.c
> +++ b/drivers/char/tpm/tpm-sysfs.c
> @@ -480,6 +480,9 @@ void tpm_sysfs_add_device(struct tpm_chip *chip)
>
> WARN_ON(chip->groups_cnt != 0);
>
> + if (tpm_is_firmware_upgrade(chip))
> + return;
> +
> if (chip->flags & TPM_CHIP_FLAG_TPM2)
> chip->groups[chip->groups_cnt++] = &tpm2_dev_group;
> else
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index a25815a6f625..4704fa553098 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -745,6 +745,12 @@ int tpm2_auto_startup(struct tpm_chip *chip)
> rc = tpm2_get_cc_attrs_tbl(chip);
>
> out:
> + if (rc == TPM2_RC_UPGRADE) {
> + dev_info(&chip->dev, "TPM in field upgrade mode, requires firmware upgrade\n");
> + chip->flags |= TPM_CHIP_FLAG_FIRMWARE_UPGRADE;
> + rc = 0;
> + }
> +
> if (rc > 0)
> rc = -ENODEV;
> return rc;
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 12d827734686..dfeb25a0362d 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -207,6 +207,7 @@ enum tpm2_return_codes {
> TPM2_RC_INITIALIZE = 0x0100, /* RC_VER1 */
> TPM2_RC_FAILURE = 0x0101,
> TPM2_RC_DISABLED = 0x0120,
> + TPM2_RC_UPGRADE = 0x012D,
> TPM2_RC_COMMAND_CODE = 0x0143,
> TPM2_RC_TESTING = 0x090A, /* RC_WARN */
> TPM2_RC_REFERENCE_H0 = 0x0910,
> @@ -278,6 +279,7 @@ enum tpm_chip_flags {
> TPM_CHIP_FLAG_HAVE_TIMEOUTS = BIT(4),
> TPM_CHIP_FLAG_ALWAYS_POWERED = BIT(5),
> TPM_CHIP_FLAG_FIRMWARE_POWER_MANAGED = BIT(6),
> + TPM_CHIP_FLAG_FIRMWARE_UPGRADE = BIT(7),
> };
>
> #define to_tpm_chip(d) container_of(d, struct tpm_chip, dev)
> @@ -399,6 +401,14 @@ static inline void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value)
> tpm_buf_append(buf, (u8 *) &value2, 4);
> }
>
> +/*
> + * Check if TPM device is in the firmware upgrade mode.
> + */
> +static inline bool tpm_is_firmware_upgrade(struct tpm_chip *chip)
> +{
> + return chip->flags & TPM_CHIP_FLAG_FIRMWARE_UPGRADE;
> +}
> +
> static inline u32 tpm2_rc_value(u32 rc)
> {
> return (rc & BIT(7)) ? rc & 0xff : rc;
> --
> 2.11.0
>
Looks good to me, thank you.
Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>
/Jarkko
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