Re: [PATCH v6] tpm: fix Atmel TPM crash caused by too frequent queries

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

> On Sep 9, 2021, at 7:08 AM, Jarkko Sakkinen <jarkko@kernel.org> wrote:
> 
> On Wed, 2021-09-08 at 02:26 -0700, Hao Wu 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>
> 
> Thanks!
> 
> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
> 
> /Jarkko

Thanks Jarkko for the review. What is the next step on my side? 

Hao