From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 49122C07E98 for ; Mon, 5 Jul 2021 05:19:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 20369613F6 for ; Mon, 5 Jul 2021 05:19:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229733AbhGEFWd (ORCPT ); Mon, 5 Jul 2021 01:22:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:45120 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229713AbhGEFWd (ORCPT ); Mon, 5 Jul 2021 01:22:33 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D1274613E7; Mon, 5 Jul 2021 05:19:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1625462397; bh=Az/D0IhuWMZAA5FollvuSsryLMhuWbsJ+/drNfuS0Qk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=a43gBB3/rdhVs3OAaur8XMDOcoBH6Xa8pfaUdF06QuGgcmpawh2+mAaRS2mr2DFu+ ajqbJorG+TqEfgfVuUg+fPHcIxfnAGiHwlWXqmZrY732F3yJOcKAvUCb1WdSKfVSB2 59I33UDrTk6oMrh3cVpnoTQ1oObizbEkiMgber79WE2pLj4vUbkrpYxp8SqfSRmZZH 8oCIyn3s1F3f5Dnl+konD+CGr//sZuBUOvxCBz4YOnocEEInQFq2djsC+omjy+ReR5 qN3imF8PjnJS6Val8HlXzi+KpcIr8c/q9J/Mf+u+72Jv04H1WcTN2rfakxGpFDavvC KGlcPtoYZ9ZUQ== Date: Mon, 5 Jul 2021 08:19:55 +0300 From: Jarkko Sakkinen To: Hao Wu 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 Subject: Re: [PATCH] tpm: fix ATMEL TPM crash caused by too frequent queries Message-ID: <20210705051955.53zoge4rkeocmfyr@kernel.org> References: <20210624053321.861-1-hao.wu@rubrik.com> <20210630042205.30051-1-hao.wu@rubrik.com> <20210702063555.q2phirfv7wxc6axu@kernel.org> <939BC11F-0905-4777-9DD7-630FC28ED205@rubrik.com> <20210702074518.64gyockmqrphbkqx@kernel.org> <559CEFEB-EE60-464B-A847-9E1C3B5F5BC4@rubrik.com> <20210702084239.svkmfw7r3y5auus3@kernel.org> <20210702115715.gyqfdk6ksgqzeenm@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On Fri, Jul 02, 2021 at 12:16:12PM -0700, Hao Wu wrote: > > > On Jul 2, 2021, at 4:57 AM, Jarkko Sakkinen 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 wrote: > >>>> > >>>> On Fri, Jul 02, 2021 at 12:33:15AM -0700, Hao Wu wrote: > >>>>> > >>>>> > >>>>>> On Jul 1, 2021, at 11:35 PM, Jarkko Sakkinen 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@rubrik.com/ > >>>>>>> > >>>>>>> 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 > >>>>>>> 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. Make things more fancy *only* when you actually need more fancy. > > 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. By saying that you are actually saying that *undocumented* semantic changes to the kernel code are fine as long as they don't change things "too much" Are you serious about this? > `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. This has absolutely nothing to do with "comfortable". It's black and white wrong. /Jarkko