Re: [PATCH v4] tpm: fix Atmel TPM crash caused by too frequent queries

[Hao Wu <hao.wu@rubrik.com>]

> On Sep 4, 2021, at 2:14 PM, Hao Wu <hao.wu@rubrik.com> wrote:
> 
> 
> 
>> On Aug 26, 2021, at 5:35 PM, Hao Wu <hao.wu@rubrik.com> wrote:
>> 
>>> On Aug 26, 2021, at 9:24 AM, Jarkko Sakkinen <jarkko@kernel.org> wrote:
>>> 
>>> On Wed, 2021-08-25 at 22:38 -0700, Hao Wu wrote:
>>>>> On Aug 14, 2021, at 3:25 PM, Hao Wu <hao.wu@rubrik.com> wrote:
>>>>> 
>>>>> The Atmel TPM 1.2 chips crash with error
>>>>> `tpm_try_transmit: send(): error -62` since kernel 4.14.
>>>>> It is observed from the kernel log after running `tpm_sealdata -z`.
>>>>> The error thrown from the command is as follows
>>>>> ```
>>>>> $ tpm_sealdata -z
>>>>> Tspi_Key_LoadKey failed: 0x00001087 - layer=tddl,
>>>>> code=0087 (135), I/O error
>>>>> ```
>>>>> 
>>>>> The issue was reproduced with the following Atmel TPM chip:
>>>>> ```
>>>>> $ tpm_version
>>>>> T0  TPM 1.2 Version Info:
>>>>> Chip Version:        1.2.66.1
>>>>> Spec Level:          2
>>>>> Errata Revision:     3
>>>>> TPM Vendor ID:       ATML
>>>>> TPM Version:         01010000
>>>>> Manufacturer Info:   41544d4c
>>>>> ```
>>>>> 
>>>>> The root cause of the issue is due to the TPM calls to msleep()
>>>>> were replaced with usleep_range() [1], which reduces
>>>>> the actual timeout. Via experiments, it is observed that
>>>>> the original msleep(5) actually sleeps for 15ms.
>>>>> Because of a known timeout issue in Atmel TPM 1.2 chip,
>>>>> the shorter timeout than 15ms can cause the error described above.
>>>>> 
>>>>> A few further changes in kernel 4.16 [2] and 4.18 [3, 4] further
>>>>> reduced the timeout to less than 1ms. With experiments,
>>>>> the problematic timeout in the latest kernel is the one
>>>>> for `wait_for_tpm_stat`.
>>>>> 
>>>>> To fix it, the patch reverts the timeout of `wait_for_tpm_stat`
>>>>> to 15ms for all Atmel TPM 1.2 chips, but leave it untouched
>>>>> for Ateml TPM 2.0 chip, and chips from other vendors.
>>>>> As explained above, the chosen 15ms timeout is
>>>>> the actual timeout before this issue introduced,
>>>>> thus the old value is used here.
>>>>> Particularly, TPM_ATML_TIMEOUT_WAIT_STAT_MIN is set to 14700us,
>>>>> TPM_ATML_TIMEOUT_WAIT_STAT_MIN is set to 15000us according to
>>>>> the existing TPM_TIMEOUT_RANGE_US (300us).
>>>>> The fixed has been tested in the system with the affected Atmel chip
>>>>> with no issues observed after boot up.
>>>>> 
>>>>> References:
>>>>> [1] 9f3fc7bcddcb tpm: replace msleep() with usleep_range() in TPM
>>>>> 1.2/2.0 generic drivers
>>>>> [2] cf151a9a44d5 tpm: reduce tpm polling delay in tpm_tis_core
>>>>> [3] 59f5a6b07f64 tpm: reduce poll sleep time in tpm_transmit()
>>>>> [4] 424eaf910c32 tpm: reduce polling time to usecs for even finer
>>>>> granularity
>>>>> 
>>>>> Fixes: 9f3fc7bcddcb ("tpm: replace msleep() with usleep_range() in TPM 1.2/2.0 generic drivers")
>>>>> Link: https://patchwork.kernel.org/project/linux-integrity/patch/20200926223150.109645-1-hao.wu@rubrik.com/
>>>>> Signed-off-by: Hao Wu <hao.wu@rubrik.com>
>>>>> ---
>>>>> v4:
>>>>> - Move timeout constants to drivers/char/tpm/tpm_tis_core.h
>>>>> - Cleanup unnecessary inline comment
>>>>> 
>>>>> v3:
>>>>> - removes unnecessary condition check in `wait_for_tpm_stat`
>>>>> 
>>>>> v2:
>>>>> - follow the existing way to define two timeouts (min and max)
>>>>> for ATMEL chip, thus keep the exact timeout logic for 
>>>>> non-ATEML chips.
>>>>> - limit the timeout increase to only ATMEL TPM 1.2 chips,
>>>>> because it is not an issue for TPM 2.0 chips yet.
>>>>> 
>>>>> Test Plan:
>>>>> - Run fixed kernel with ATMEL TPM chips and see crash
>>>>> has been fixed.
>>>>> - Run fixed kernel with non-ATMEL TPM chips, and confirm
>>>>> the timeout has not been changed.
>>>>> 
>>>>> drivers/char/tpm/tpm_tis_core.c | 13 +++++++++++--
>>>>> drivers/char/tpm/tpm_tis_core.h |  2 ++
>>>>> include/linux/tpm.h             |  3 +++
>>>>> 3 files changed, 16 insertions(+), 2 deletions(-)
>>>>> 
>>>>> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
>>>>> index 55b9d3965ae1..24605f100e96 100644
>>>>> --- a/drivers/char/tpm/tpm_tis_core.c
>>>>> +++ b/drivers/char/tpm/tpm_tis_core.c
>>>>> @@ -80,8 +80,8 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
>>>>> 		}
>>>>> 	} else {
>>>>> 		do {
>>>>> -			usleep_range(TPM_TIMEOUT_USECS_MIN,
>>>>> -				     TPM_TIMEOUT_USECS_MAX);
>>>>> +			usleep_range(chip->timeout_wait_stat_min,
>>>>> +				     chip->timeout_wait_stat_max);
>>>>> 			status = chip->ops->status(chip);
>>>>> 			if ((status & mask) == mask)
>>>>> 				return 0;
>>>>> @@ -934,6 +934,8 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>>>>> 	chip->timeout_b = msecs_to_jiffies(TIS_TIMEOUT_B_MAX);
>>>>> 	chip->timeout_c = msecs_to_jiffies(TIS_TIMEOUT_C_MAX);
>>>>> 	chip->timeout_d = msecs_to_jiffies(TIS_TIMEOUT_D_MAX);
>>>>> +	chip->timeout_wait_stat_min = TPM_TIMEOUT_USECS_MIN;
>>>>> +	chip->timeout_wait_stat_max = TPM_TIMEOUT_USECS_MAX;
>>>>> 	priv->phy_ops = phy_ops;
>>>>> 	dev_set_drvdata(&chip->dev, priv);
>>>>> 
>>>>> @@ -983,6 +985,13 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>>>>> 
>>>>> 	priv->manufacturer_id = vendor;
>>>>> 
>>>>> +	if (priv->manufacturer_id == TPM_VID_ATML &&
>>>>> +		!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
>>>>> +		/* If TPM chip is 1.2 ATMEL chip, timeout need to be relaxed*/
>>>>> +		chip->timeout_wait_stat_min = TPM_ATML_TIMEOUT_WAIT_STAT_MIN;
>>>>> +		chip->timeout_wait_stat_max = TPM_ATML_TIMEOUT_WAIT_STAT_MAX;
>>>>> +	}
>>>>> +
>>>>> 	rc = tpm_tis_read8(priv, TPM_RID(0), &rid);
>>>>> 	if (rc < 0)
>>>>> 		goto out_err;
>>>>> diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
>>>>> index 9b2d32a59f67..2e431beb44f7 100644
>>>>> --- a/drivers/char/tpm/tpm_tis_core.h
>>>>> +++ b/drivers/char/tpm/tpm_tis_core.h
>>>>> @@ -54,6 +54,8 @@ enum tis_defaults {
>>>>> 	TIS_MEM_LEN = 0x5000,
>>>>> 	TIS_SHORT_TIMEOUT = 750,	/* ms */
>>>>> 	TIS_LONG_TIMEOUT = 2000,	/* 2 sec */
>>>>> +	TPM_ATML_TIMEOUT_WAIT_STAT_MIN = 14700,	/* usecs */
>>>>> +	TPM_ATML_TIMEOUT_WAIT_STAT_MAX = 15000,	/* usecs */
>>>>> };
>>> 
>>> I'd prefer TIS_TIMEOUT_{MIN, MAX}_ATML. I.e. no "WAIT_STAT" and without "TPM_"
>>> to be consistent with other constants here.
>> Ok will do
>>> 
>>>>> 
>>>>> /* Some timeout values are needed before it is known whether the chip is
>>>>> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
>>>>> index aa11fe323c56..171b9102c976 100644
>>>>> --- a/include/linux/tpm.h
>>>>> +++ b/include/linux/tpm.h
>>>>> @@ -150,6 +150,8 @@ struct tpm_chip {
>>>>> 	bool timeout_adjusted;
>>>>> 	unsigned long duration[TPM_NUM_DURATIONS]; /* jiffies */
>>>>> 	bool duration_adjusted;
>>>>> +	unsigned int timeout_wait_stat_min; /* usecs */
>>>>> +	unsigned int timeout_wait_stat_max; /* usecs */
>>> 
>>> Please rename as timeout_{min, max}.
>> Ok will do
To be honest, this naming could be misleading, because the timeout here only applies to wait_stat use case. 
But I will just follow you suggestion anyway.

Hao

>>> 
>>> And I think tpm_chip is wrong place to put them as they are TIS
>>> specific, i.e. they should be in tpm_tis_data.
>> Sorry, I am not familiar with tpm_tis_data, could tell the the place that you want me to put the var? 
>> I think I may have hard time to move forward according toward this comment due to bandwidth constraints.
>> Some helps would be appreciated. 
>> 
>> Is tpm_tis_data something specific to a chip instance ? Given the values are tied to chip,
>> we need chip specific instance to make this work.
> 
> Hi Jarkko, I have checked about your proposal a bit. It look slike we need to 
> Run “struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev)” in every wait_for_tpm_stat call. Would this be a performance concern ? 
> If we cache this in tpm_chip instance, it is not the case. 
> 
> Please let me know your thought.
> 
> Hao 
> 
>>> 
>>>>> 
>>>>> 	struct dentry *bios_dir[TPM_NUM_EVENT_LOG_FILES];
>>>>> 
>>>>> @@ -269,6 +271,7 @@ enum tpm2_cc_attrs {
>>>>> #define TPM_VID_INTEL    0x8086
>>>>> #define TPM_VID_WINBOND  0x1050
>>>>> #define TPM_VID_STM      0x104A
>>>>> +#define TPM_VID_ATML     0x1114
>>>>> 
>>>>> enum tpm_chip_flags {
>>>>> 	TPM_CHIP_FLAG_TPM2		= BIT(1),
>>>>> -- 
>>>>> 2.29.0.vfs.0.0
>>>>> 
>>>> 
>>>> Just kindly remind this code review in case it has been missed somehow
>>> 
>>> I'm sorry, my bad. I managed to somehow miss this. Might be because
>>> I've been recently reorganizing my email accounts. And thanks for
>>> pinging so that I spotted it.
>> No worries, thanks for quick response!
>> 
>>> 
>>>> Thanks
>>>> Hao
>>> 
>>> /Jarkko
>> 
>> Hao
>