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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 6D178C7618F for ; Thu, 18 Jul 2019 16:11:35 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 0B21421019 for ; Thu, 18 Jul 2019 16:11:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0B21421019 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=virtuozzo.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 96DFB8E0009; Thu, 18 Jul 2019 12:11:34 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8F79A8E0007; Thu, 18 Jul 2019 12:11:34 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7991F8E0009; Thu, 18 Jul 2019 12:11:34 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-lj1-f199.google.com (mail-lj1-f199.google.com [209.85.208.199]) by kanga.kvack.org (Postfix) with ESMTP id 0F0198E0007 for ; Thu, 18 Jul 2019 12:11:34 -0400 (EDT) Received: by mail-lj1-f199.google.com with SMTP id e14so6264611ljj.3 for ; Thu, 18 Jul 2019 09:11:33 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:subject:to:cc :references:from:message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=Ka7PIt6i9Q88JwccYuiYHqGAECqE20Y+n7xYlOq9DlY=; b=saxvuBri8tTvW6Aar0yJnSMY7VVumHuyRSdoQn/jF3vOnwGDkqzgpv88d+MLyyv+bv ehmZNPPXpOAa+XT2xQc+AX1Zk2FLkzqpyAHut4ZV+4/GUVBZejKg/X01vtlhd4eOQQ5T vBbf5aiJC0wh3vQCY1Xaz8s6ol0tlZpofaqwg9knqjhYwi5cvdi6a9GID7/CN2xg9Qa3 ikHiZZ1YsYkgcfgT2U1MDCVfweHjz2XPOYJ7zpusv/x6PvnoZU+1rwtd6JF0flN1wWhT 7skOx646hiwgYUw/3d+F5ELIuQ2XHjGae92UStdm4KwjSA7zL8DOwKolCTomVHumkJrf C2Iw== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of aryabinin@virtuozzo.com designates 185.231.240.75 as permitted sender) smtp.mailfrom=aryabinin@virtuozzo.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=virtuozzo.com X-Gm-Message-State: APjAAAX6+WfOtpZqF5zHHnH2ExYxfhe9GicvYVZbhVCN6RYJwM6uxWV1 TqnFhPnXDJYzf5fjSdYcKFZBzHJ0Xo2GwxQF/oVb3+IDLmxVhuvnbHm/mBuKxIGoV3hv4wKVGtM 5QNaPvbgwXGa6abmbZz4Ex3VwNAmXgQZpq/V34BCT/Ph1frNZKTQqVCWwRT+n3k38bQ== X-Received: by 2002:a2e:7013:: with SMTP id l19mr25169609ljc.141.1563466293314; Thu, 18 Jul 2019 09:11:33 -0700 (PDT) X-Google-Smtp-Source: APXvYqzUUjTkGTT6FUVR5mppasJSMO8bcPn2Ou11FW/vWVn7iNIBIYdqyh7adGti/V1CFLfyfb3r X-Received: by 2002:a2e:7013:: with SMTP id l19mr25169554ljc.141.1563466292267; Thu, 18 Jul 2019 09:11:32 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1563466292; cv=none; d=google.com; s=arc-20160816; b=b9LJDdTYcnlp00NPhMF/gpYQtmNFCAwbT+un50Ne6rQOCL7NHDiPtOPlmOQWO9ifab I5dKk3c53y287WkCZ/4EoMyAXn94+zNAUNW+3WppqMTGZDIQWOak8bNhsNFb/N6vatfd Dj57ecibaXb4uH5NGqU9Rq0twHz69TQQXTsTEGui5eJVjBQxl7IGz9vt5sQMAP0WIGZQ pEojAxOnqn2r43sZL9YTUnXSKfwKIXLUU/H2YR8ujIv/FMp42lgKQYvfwpdS9+2lMp3h JApwqzVUA8ToFqby8qCkdHH9+99lqjThtStotXiwK9q7kPssDhMM6gNIkevxs5s8Wr8N RVtg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:from:references:cc:to:subject; bh=Ka7PIt6i9Q88JwccYuiYHqGAECqE20Y+n7xYlOq9DlY=; b=HB/qPFRPXS1m4lE9T8yY521JKd1vWrNbpDc51QEvOOKw1lSmIW7OeAXWwcSTc5tbS0 qjeGjFaueJG2Thmc3s3c7xnK4+9P2jQkcEEChcV6AX+RFwc7cGNLQEPDvrPuuEQ2ZFbh oEStk59KjasVAX0Wa22i27eIiL3YxKaw3gwktBPpZVPjA9F6+o8Ak5fDy14dElTDalla pDKPbwWMFYCPwdnyJezKoQXRLRIEvGxGIO0fDbkbKmXnOmFxfRYEihMJILoro6BTTTtg jv8kLoc+Klpr6FDX3AwwsksL8WSPMa5R7ImVNh0NnBqydLsWFAHp0l0uBQbsTOCvANWg Uvtg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of aryabinin@virtuozzo.com designates 185.231.240.75 as permitted sender) smtp.mailfrom=aryabinin@virtuozzo.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=virtuozzo.com Received: from relay.sw.ru (relay.sw.ru. [185.231.240.75]) by mx.google.com with ESMTPS id 132si20850659lfi.55.2019.07.18.09.11.32 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Jul 2019 09:11:32 -0700 (PDT) Received-SPF: pass (google.com: domain of aryabinin@virtuozzo.com designates 185.231.240.75 as permitted sender) client-ip=185.231.240.75; Authentication-Results: mx.google.com; spf=pass (google.com: domain of aryabinin@virtuozzo.com designates 185.231.240.75 as permitted sender) smtp.mailfrom=aryabinin@virtuozzo.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=virtuozzo.com Received: from [172.16.25.12] by relay.sw.ru with esmtp (Exim 4.92) (envelope-from ) id 1ho902-00080M-Ln; Thu, 18 Jul 2019 19:11:18 +0300 Subject: Re: [PATCH v3] kasan: add memory corruption identification for software tag-based mode To: Walter Wu Cc: Dmitry Vyukov , Alexander Potapenko , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Matthias Brugger , Martin Schwidefsky , Arnd Bergmann , Vasily Gorbik , Andrey Konovalov , "Jason A . Donenfeld" , Miles Chen , kasan-dev , LKML , Linux-MM , Linux ARM , linux-mediatek@lists.infradead.org, wsd_upstream References: <20190613081357.1360-1-walter-zh.wu@mediatek.com> <1560447999.15814.15.camel@mtksdccf07> <1560479520.15814.34.camel@mtksdccf07> <1560744017.15814.49.camel@mtksdccf07> <1560774735.15814.54.camel@mtksdccf07> <1561974995.18866.1.camel@mtksdccf07> <1562640832.9077.32.camel@mtksdccf07> <1562839579.5846.12.camel@mtksdccf07> <37897fb7-88c1-859a-dfcc-0a5e89a642e0@virtuozzo.com> <1563160001.4793.4.camel@mtksdccf07> From: Andrey Ryabinin Message-ID: <9ab1871a-2605-ab34-3fd3-4b44a0e17ab7@virtuozzo.com> Date: Thu, 18 Jul 2019 19:11:21 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <1563160001.4793.4.camel@mtksdccf07> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 7/15/19 6:06 AM, Walter Wu wrote: > On Fri, 2019-07-12 at 13:52 +0300, Andrey Ryabinin wrote: >> >> On 7/11/19 1:06 PM, Walter Wu wrote: >>> On Wed, 2019-07-10 at 21:24 +0300, Andrey Ryabinin wrote: >>>> >>>> On 7/9/19 5:53 AM, Walter Wu wrote: >>>>> On Mon, 2019-07-08 at 19:33 +0300, Andrey Ryabinin wrote: >>>>>> >>>>>> On 7/5/19 4:34 PM, Dmitry Vyukov wrote: >>>>>>> On Mon, Jul 1, 2019 at 11:56 AM Walter Wu wrote: >>>> >>>>>>> >>>>>>> Sorry for delays. I am overwhelm by some urgent work. I afraid to >>>>>>> promise any dates because the next week I am on a conference, then >>>>>>> again a backlog and an intern starting... >>>>>>> >>>>>>> Andrey, do you still have concerns re this patch? This change allows >>>>>>> to print the free stack. >>>>>> >>>>>> I 'm not sure that quarantine is a best way to do that. Quarantine is made to delay freeing, but we don't that here. >>>>>> If we want to remember more free stacks wouldn't be easier simply to remember more stacks in object itself? >>>>>> Same for previously used tags for better use-after-free identification. >>>>>> >>>>> >>>>> Hi Andrey, >>>>> >>>>> We ever tried to use object itself to determine use-after-free >>>>> identification, but tag-based KASAN immediately released the pointer >>>>> after call kfree(), the original object will be used by another >>>>> pointer, if we use object itself to determine use-after-free issue, then >>>>> it has many false negative cases. so we create a lite quarantine(ring >>>>> buffers) to record recent free stacks in order to avoid those false >>>>> negative situations. >>>> >>>> I'm telling that *more* than one free stack and also tags per object can be stored. >>>> If object reused we would still have information about n-last usages of the object. >>>> It seems like much easier and more efficient solution than patch you proposing. >>>> >>> To make the object reused, we must ensure that no other pointers uses it >>> after kfree() release the pointer. >>> Scenario: >>> 1). The object reused information is valid when no another pointer uses >>> it. >>> 2). The object reused information is invalid when another pointer uses >>> it. >>> Do you mean that the object reused is scenario 1) ? >>> If yes, maybe we can change the calling quarantine_put() location. It >>> will be fully use that quarantine, but at scenario 2) it looks like to >>> need this patch. >>> If no, maybe i miss your meaning, would you tell me how to use invalid >>> object information? or? >>> >> >> >> KASAN keeps information about object with the object, right after payload in the kasan_alloc_meta struct. >> This information is always valid as long as slab page allocated. Currently it keeps only one last free stacktrace. >> It could be extended to record more free stacktraces and also record previously used tags which will allow you >> to identify use-after-free and extract right free stacktrace. > > Thanks for your explanation. > > For extend slub object, if one record is 9B (sizeof(u8)+ sizeof(struct > kasan_track)) and add five records into slub object, every slub object > may add 45B usage after the system runs longer. > Slub object number is easy more than 1,000,000(maybe it may be more > bigger), then the extending object memory usage should be 45MB, and > unfortunately it is no limit. The memory usage is more bigger than our > patch. No, it's not necessarily more. And there are other aspects to consider such as performance, how simple reliable the code is. > > We hope tag-based KASAN advantage is smaller memory usage. If it’s > possible, we should spend less memory in order to identify > use-after-free. Would you accept our patch after fine tune it? Sure, if you manage to fix issues and demonstrate that performance penalty of your patch is close to zero.