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[73.231.56.47]) by smtp.gmail.com with ESMTPSA id m16sm2641550pfo.152.2021.07.09.12.23.10 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 09 Jul 2021 12:23:16 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.60.0.2.21\)) Subject: Re: [PATCH v2] tpm: fix Atmel TPM crash caused by too frequent queries From: Hao Wu In-Reply-To: <20210709174707.z2ap7czu2lldeavw@kernel.org> Date: Fri, 9 Jul 2021 12:23:07 -0700 Cc: Shrihari Kalkar , Seungyeop Han , Anish Jhaveri , peterhuewe@gmx.de, jgg@ziepe.ca, linux-integrity@vger.kernel.org, Paul Menzel , Ken Goldman , zohar@linux.vnet.ibm.com, why2jjj.linux@gmail.com, Hamza Attak , gregkh@linuxfoundation.org, arnd@arndb.de, Nayna , James.Bottomley@hansenpartnership.com Content-Transfer-Encoding: quoted-printable Message-Id: References: <20210630042205.30051-1-hao.wu@rubrik.com> <20210709044028.77278-1-hao.wu@rubrik.com> <20210709174707.z2ap7czu2lldeavw@kernel.org> To: Jarkko Sakkinen X-Mailer: Apple Mail (2.3654.60.0.2.21) Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org > On Jul 9, 2021, at 10:47 AM, Jarkko Sakkinen = wrote: >=20 > On Thu, Jul 08, 2021 at 09:40:28PM -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=3Dtddl, >> code=3D0087 (135), I/O error >> ``` >>=20 >> 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 >> ``` >>=20 >> 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. >>=20 >> 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`. >>=20 >> 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. >>=20 >> 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 >>=20 >> 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 >> --- >> This version (v2) has following changes on top of the last (v1): >> - follow the existing way to define two timeouts (min and max) >> for ATMEL chip, thus keep the exact timeout logic for=20 >> 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. >>=20 >> 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. >>=20 >> drivers/char/tpm/tpm.h | 6 ++++-- >> drivers/char/tpm/tpm_tis_core.c | 23 +++++++++++++++++++++-- >> include/linux/tpm.h | 3 +++ >> 3 files changed, 28 insertions(+), 4 deletions(-) >>=20 >> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h >> index 283f78211c3a..6de1b44c4aab 100644 >> --- a/drivers/char/tpm/tpm.h >> +++ b/drivers/char/tpm/tpm.h >> @@ -41,8 +41,10 @@ enum tpm_timeout { >> TPM_TIMEOUT_RETRY =3D 100, /* msecs */ >> TPM_TIMEOUT_RANGE_US =3D 300, /* usecs */ >> TPM_TIMEOUT_POLL =3D 1, /* msecs */ >> - TPM_TIMEOUT_USECS_MIN =3D 100, /* usecs */ >> - TPM_TIMEOUT_USECS_MAX =3D 500 /* usecs */ >> + TPM_TIMEOUT_USECS_MIN =3D 100, /* usecs */ >> + TPM_TIMEOUT_USECS_MAX =3D 500, /* usecs */ >> + TPM_ATML_TIMEOUT_WAIT_STAT_MIN =3D 14700, /* usecs */ >> + TPM_ATML_TIMEOUT_WAIT_STAT_MAX =3D 15000 /* usecs */ >> }; >>=20 >> /* TPM addresses */ >> diff --git a/drivers/char/tpm/tpm_tis_core.c = b/drivers/char/tpm/tpm_tis_core.c >> index 55b9d3965ae1..ae27d66fdd94 100644 >> --- a/drivers/char/tpm/tpm_tis_core.c >> +++ b/drivers/char/tpm/tpm_tis_core.c >> @@ -80,8 +80,17 @@ static int wait_for_tpm_stat(struct tpm_chip = *chip, u8 mask, >> } >> } else { >> do { >> - usleep_range(TPM_TIMEOUT_USECS_MIN, >> - TPM_TIMEOUT_USECS_MAX); >> + /* this code path could be executed before >> + * timeouts initialized in chip instance. >> + */ >> + if (chip->timeout_wait_stat_min && >> + chip->timeout_wait_stat_max) >> + = usleep_range(chip->timeout_wait_stat_min, >> + = chip->timeout_wait_stat_max); >> + else >> + usleep_range(TPM_TIMEOUT_USECS_MIN, >> + TPM_TIMEOUT_USECS_MAX); >=20 > This starts to look otherwise fine but you don't need this condition. > Just initialize variables to TPM_TIMEOUT_USECS_{MIN, MAX} for = non-Atmel. Not sure I got your point or not. We have discussed this question a few = rounds before, I answered you about this. This check is required because before the = time of=20 Initialization in the code I added in `tpm_tis_core_init` ``` + chip->timeout_wait_stat_min =3D TPM_TIMEOUT_USECS_MIN; + chip->timeout_wait_stat_max =3D TPM_TIMEOUT_USECS_MAX; ``` The func `wait_for_tpm_stat` runs, we need the condition to fall back to = avoid system startup crash. Let me know if this makes sense. If needed, I can do another confirm. > /Jarkko Hao