> On Jul 2, 2021, at 4:57 AM, Jarkko Sakkinen <jarkko@xxxxxxxxxx> wrote: > > On Fri, Jul 02, 2021 at 11:42:39AM +0300, Jarkko Sakkinen wrote: >> On Fri, Jul 02, 2021 at 12:59:18AM -0700, Hao Wu wrote: >>>> On Jul 2, 2021, at 12:45 AM, Jarkko Sakkinen <jarkko@xxxxxxxxxx> wrote: >>>> >>>> On Fri, Jul 02, 2021 at 12:33:15AM -0700, Hao Wu wrote: >>>>> >>>>> >>>>>> On Jul 1, 2021, at 11:35 PM, Jarkko Sakkinen <jarkko@xxxxxxxxxx> wrote: >>>>>> >>>>>> On Tue, Jun 29, 2021 at 09:22:05PM -0700, Hao Wu wrote: >>>>>>> This is a fix for the ATMEL TPM crash bug reported in >>>>>>> https://patchwork.kernel.org/project/linux-integrity/patch/20200926223150.109645-1-hao.wu@xxxxxxxxxx/ >>>>>>> >>>>>>> According to the discussions in the original thread, >>>>>>> we don't want to revert the timeout of wait_for_tpm_stat >>>>>>> for non-ATMEL chips, which brings back the performance cost. >>>>>>> For investigation and analysis of why wait_for_tpm_stat >>>>>>> caused the issue, and how the regression was introduced, >>>>>>> please read the original thread above. >>>>>>> >>>>>>> Thus the proposed fix here is to only revert the timeout >>>>>>> for ATMEL chips by checking the vendor ID. >>>>>>> >>>>>>> Signed-off-by: Hao Wu <hao.wu@xxxxxxxxxx> >>>>>>> Fixes: 9f3fc7bcddcb ("tpm: replace msleep() with usleep_range() in TPM 1.2/2.0 generic drivers") >>>>>> >>>>>> Fixes tag should be before SOB. >>>>>> >>>>>>> --- >>>>>>> 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.h | 9 ++++++++- >>>>>>> drivers/char/tpm/tpm_tis_core.c | 19 +++++++++++++++++-- >>>>>>> include/linux/tpm.h | 2 ++ >>>>>>> 3 files changed, 27 insertions(+), 3 deletions(-) >>>>>>> >>>>>>> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h >>>>>>> index 283f78211c3a..bc6aa7f9e119 100644 >>>>>>> --- a/drivers/char/tpm/tpm.h >>>>>>> +++ b/drivers/char/tpm/tpm.h >>>>>>> @@ -42,7 +42,9 @@ enum tpm_timeout { >>>>>>> TPM_TIMEOUT_RANGE_US = 300, /* usecs */ >>>>>>> TPM_TIMEOUT_POLL = 1, /* msecs */ >>>>>>> TPM_TIMEOUT_USECS_MIN = 100, /* usecs */ >>>>>>> - TPM_TIMEOUT_USECS_MAX = 500 /* usecs */ >>>>>>> + TPM_TIMEOUT_USECS_MAX = 500, /* usecs */ >>>>>> >>>>>> What is this change? >>>>> Need to add the tailing comma >>>>> >>>>>> >>>>>>> + TPM_TIMEOUT_WAIT_STAT = 500, /* usecs */ >>>>>>> + TPM_ATML_TIMEOUT_WAIT_STAT = 15000 /* usecs */ >>>>>>> }; >>>>>>> >>>>>>> /* TPM addresses */ >>>>>>> @@ -189,6 +191,11 @@ static inline void tpm_msleep(unsigned int delay_msec) >>>>>>> delay_msec * 1000); >>>>>>> }; >>>>>>> >>>>>>> +static inline void tpm_usleep(unsigned int delay_usec) >>>>>>> +{ >>>>>>> + usleep_range(delay_usec - TPM_TIMEOUT_RANGE_US, delay_usec); >>>>>>> +}; >>>>>> >>>>>> Please remove this, and open code. >>>>> Ok, will do >>>>> >>>>>>> + >>>>>>> int tpm_chip_start(struct tpm_chip *chip); >>>>>>> void tpm_chip_stop(struct tpm_chip *chip); >>>>>>> struct tpm_chip *tpm_find_get_ops(struct tpm_chip *chip); >>>>>>> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c >>>>>>> index 55b9d3965ae1..9ddd4edfe1c2 100644 >>>>>>> --- a/drivers/char/tpm/tpm_tis_core.c >>>>>>> +++ b/drivers/char/tpm/tpm_tis_core.c >>>>>>> @@ -80,8 +80,12 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask, >>>>>>> } >>>>>>> } else { >>>>>>> do { >>>>>>> - usleep_range(TPM_TIMEOUT_USECS_MIN, >>>>>>> - TPM_TIMEOUT_USECS_MAX); >>>>>>> + if (chip->timeout_wait_stat && >>>>>>> + chip->timeout_wait_stat >= TPM_TIMEOUT_WAIT_STAT) { >>>>>>> + tpm_usleep((unsigned int)(chip->timeout_wait_stat)); >>>>>>> + } else { >>>>>>> + tpm_usleep((unsigned int)(TPM_TIMEOUT_WAIT_STAT)); >>>>>>> + } >>>>>> >>>>>> Invalid use of braces. Please read >>>>>> >>>>>> https://www.kernel.org/doc/html/v5.13/process/coding-style.html >>>>>> >>>>>> Why do you have to use this field conditionally anyway? Why doesn't >>>>>> it always contain a legit value? >>>>> The field is legit now, but doesn’t hurt to do addition check for robustness >>>>> to ensure no crash ? Just in case the value is updated below TPM_TIMEOUT_WAIT_STAT ? >>>>> >>>>> Can remove if we think it is not needed. >>>> >>>> A simple question: why you use it conditionally? Can the field contain invalid value? >>>> >>> There are two checks >>> - chip->timeout_wait_stat >= TPM_TIMEOUT_WAIT_STAT >>> It could be invalid when future developer set it to some value less than `TPM_TIMEOUT_USECS_MIN`, >>> and crash the usleep >> >> I don't understand this. Why you don't set to appropriate value? Ok, fair enough, I assume developers will test it anyway to ensure no crash. Will remove this check. > What you should do, is to define two fields: > > - tpm_timeout_min > - tpm_timeout_max > > And initialize these to TPM_TIMEOUT_USECS_MIN and TPM_TIMEOUT_USECS_MAX. > > Then fixup those for Atmel (with a simple if-statement, switch-case is > overkill). Switch was more for extensibility when other vendor has similar issue, but we can refactor when needed in the future. I can use if-statement for now. > The way you work out things right now is broken: > > 1. Before for non-Atmel: usleep_range(100, 500) > 2. After for non-Atmel: usleep_range(200, 500) I realized this in day-1, I think this range change does not matter much. `TPM_TIMEOUT_RANGE_US=300` is already used in the codebase, I assume people define such if for general use cases for usleep_range in TPM But we can add two fields if that makes us more comfortable to strictly follow the current code semantically. > I.e. the patch changes code semantically that it should not touch in the > first place. > > /Jarkko Hao
