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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable 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 8EF5BC282CE for ; Mon, 11 Feb 2019 16:28:21 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 32FFC218F0 for ; Mon, 11 Feb 2019 16:28:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 32FFC218F0 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 BF6F28E00FB; Mon, 11 Feb 2019 11:28:20 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id BA75E8E00F6; Mon, 11 Feb 2019 11:28:20 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A95C28E00FB; Mon, 11 Feb 2019 11:28:20 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from mail-lj1-f200.google.com (mail-lj1-f200.google.com [209.85.208.200]) by kanga.kvack.org (Postfix) with ESMTP id 3FC0B8E00F6 for ; Mon, 11 Feb 2019 11:28:20 -0500 (EST) Received: by mail-lj1-f200.google.com with SMTP id t22-v6so2960138lji.14 for ; Mon, 11 Feb 2019 08:28:20 -0800 (PST) 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=CXabaxyjDT3D6OWec+4Nlzm7+oYSKaftIBCUycXZI2o=; b=tJw78CPAUY2T2LZkSsxksUKZEMDz2dKwuALRIJJPC56hQMh2eoOBDxNS7s0NCsyoSh DJbHnAaMY2T8YYxZnw3oEBuhOodpoHEVd2h1/8P49AQ+MPwQUakBbMIGiD43Qwp1hvoL rEnQ3rcEBiIK/jxKbvu8yAS6t4VlD/yK0PlVOI9vxq7++3Eghw35XrOySplaetAp8rGW RgQAi3F0wQ+Tn71+n1JfIT6GYNzi+OfxqVmIEhbCBhQKkUiuzwHQw9GKqJ4en/JIiBX8 VGbGTGP2wb1e6rb+e06aTciLQ46r9I5oLjSkLkI09RHtf7Z+S8ZCIilhU5PuSG4RgHhG 3NlQ== 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: AHQUAubuAAOg6AlJrFVyxHwp0SXpDabP8mXuOSvEjkyeU8+qSgIPOD7U lz25cQe0xtriffWfAXCl1LFEJQyrKgZOgC7Rym8lHWM/SS5mhT3BEaBtqjJEIjlsCW6FOrtmSoy AJUVQ7cbnbH3oDYocBimacj2ikUuLwGd2GLvXsbia0eUt7rQjjS70t62anT7V4DYVIQ== X-Received: by 2002:a2e:4503:: with SMTP id s3-v6mr21635945lja.44.1549902499487; Mon, 11 Feb 2019 08:28:19 -0800 (PST) X-Google-Smtp-Source: AHgI3IbVNlOG89VoCS+eFHUydvLDfN/1cmpjQnmQSkvSPLL68bCjKerI52EgZi2RMjBXbAvAaQSx X-Received: by 2002:a2e:4503:: with SMTP id s3-v6mr21635885lja.44.1549902498091; Mon, 11 Feb 2019 08:28:18 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1549902498; cv=none; d=google.com; s=arc-20160816; b=UmTNSaM4qEzn+bXm1AGMIiPslzCQxM3x4CN7moM2HITXiVomqnLY7MXs2Uw2s+5AZ2 nxWUEraCKMJBX/roH9CTcjzkMuoerdjsEYQstlbvHVJ1awEeSfJ3Wbt7PRgM3JZsxO06 HCZ3BTI0PDr3C0zgVK652pj3+/kwvPr+4VZ4Ni/s4lWLy6Cc7ZxNJ8MbiuHh5ZjU4xbU ZReYp6zUzSHXniCNTx7bkEvyoEQqAAcyHT7g4oZu6B7pkcvh5lccm0W7AQzwSx0r6s8W flptkzAoVmioNbVEbtr2quboM0ByDMF8dTqG/FprFC45qOoeXdPv+zo3mnvv1fFWf6Z+ IDIw== 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=CXabaxyjDT3D6OWec+4Nlzm7+oYSKaftIBCUycXZI2o=; b=JWCULkmC6xXGvM8Y8ui1ntbV4PArWPoQCCcSzWdbe6ZjJQ4UrtOpt+eIFKc+PXVw9X Awx+Z03G8y8UJ0QM7rY9KtXgoazYmRT98X0e7fkCBFK6IIM2xMo/iyFEfTXlxPQ33nGd ObT6ghBWpP1S76MY+GI+b0Hgr1/KMVKz+Tyv5hCJMVb6MFZNCb4JGs20zJc+37ovfhzc GflgXxQ3XSP6bSr88nLoYgsqN6HJz64UXfj+Z3jdxW9NorOTrSqgx7eKnm8z/JftI4hM toS28NFBeUrJ1R4J04us5mzc0mgJD8jj7ZD6cTJ1izNa+miMb3cjvrQs+iR2MPy9x0gs U5fQ== 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 i13si9479318lfc.125.2019.02.11.08.28.17 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Feb 2019 08:28:18 -0800 (PST) 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 4.91) (envelope-from ) id 1gtERF-0001Xi-Kx; Mon, 11 Feb 2019 19:28:09 +0300 Subject: Re: [PATCH v4 3/3] powerpc/32: Add KASAN support To: Andrey Konovalov , christophe leroy Cc: Daniel Axtens , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Nicholas Piggin , "Aneesh Kumar K.V" , Alexander Potapenko , Dmitry Vyukov , Linux Memory Management List , PowerPC , LKML , kasan-dev References: <1f5629e03181d0e30efc603f00dad78912991a45.1548166824.git.christophe.leroy@c-s.fr> <87ef8i45km.fsf@dja-thinkpad.axtens.net> <69720148-fd19-0810-5a1d-96c45e2ec00c@c-s.fr> From: Andrey Ryabinin Message-ID: <805fbf9d-a10f-03e0-aa52-6f6bd16059b9@virtuozzo.com> Date: Mon, 11 Feb 2019 19:28:31 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: 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 2/11/19 3:25 PM, Andrey Konovalov wrote: > On Sat, Feb 9, 2019 at 12:55 PM christophe leroy > wrote: >> >> Hi Andrey, >> >> Le 08/02/2019 à 18:40, Andrey Konovalov a écrit : >>> On Fri, Feb 8, 2019 at 6:17 PM Christophe Leroy wrote: >>>> >>>> Hi Daniel, >>>> >>>> Le 08/02/2019 à 17:18, Daniel Axtens a écrit : >>>>> Hi Christophe, >>>>> >>>>> I've been attempting to port this to 64-bit Book3e nohash (e6500), >>>>> although I think I've ended up with an approach more similar to Aneesh's >>>>> much earlier (2015) series for book3s. >>>>> >>>>> Part of this is just due to the changes between 32 and 64 bits - we need >>>>> to hack around the discontiguous mappings - but one thing that I'm >>>>> particularly puzzled by is what the kasan_early_init is supposed to do. >>>> >>>> It should be a problem as my patch uses a 'for_each_memblock(memory, >>>> reg)' loop. >>>> >>>>> >>>>>> +void __init kasan_early_init(void) >>>>>> +{ >>>>>> + unsigned long addr = KASAN_SHADOW_START; >>>>>> + unsigned long end = KASAN_SHADOW_END; >>>>>> + unsigned long next; >>>>>> + pmd_t *pmd = pmd_offset(pud_offset(pgd_offset_k(addr), addr), addr); >>>>>> + int i; >>>>>> + phys_addr_t pa = __pa(kasan_early_shadow_page); >>>>>> + >>>>>> + BUILD_BUG_ON(KASAN_SHADOW_START & ~PGDIR_MASK); >>>>>> + >>>>>> + if (early_mmu_has_feature(MMU_FTR_HPTE_TABLE)) >>>>>> + panic("KASAN not supported with Hash MMU\n"); >>>>>> + >>>>>> + for (i = 0; i < PTRS_PER_PTE; i++) >>>>>> + __set_pte_at(&init_mm, (unsigned long)kasan_early_shadow_page, >>>>>> + kasan_early_shadow_pte + i, >>>>>> + pfn_pte(PHYS_PFN(pa), PAGE_KERNEL_RO), 0); >>>>>> + >>>>>> + do { >>>>>> + next = pgd_addr_end(addr, end); >>>>>> + pmd_populate_kernel(&init_mm, pmd, kasan_early_shadow_pte); >>>>>> + } while (pmd++, addr = next, addr != end); >>>>>> +} >>>>> >>>>> As far as I can tell it's mapping the early shadow page, read-only, over >>>>> the KASAN_SHADOW_START->KASAN_SHADOW_END range, and it's using the early >>>>> shadow PTE array from the generic code. >>>>> >>>>> I haven't been able to find an answer to why this is in the docs, so I >>>>> was wondering if you or anyone else could explain the early part of >>>>> kasan init a bit better. >>>> >>>> See https://www.kernel.org/doc/html/latest/dev-tools/kasan.html for an >>>> explanation of the shadow. >>>> >>>> When shadow is 0, it means the memory area is entirely accessible. >>>> >>>> It is necessary to setup a shadow area as soon as possible because all >>>> data accesses check the shadow area, from the begining (except for a few >>>> files where sanitizing has been disabled in Makefiles). >>>> >>>> Until the real shadow area is set, all access are granted thanks to the >>>> zero shadow area beeing for of zeros. >>> >>> Not entirely correct. kasan_early_init() indeed maps the whole shadow >>> memory range to the same kasan_early_shadow_page. However as kernel >>> loads and memory gets allocated this shadow page gets rewritten with >>> non-zero values by different KASAN allocator hooks. Since these values >>> come from completely different parts of the kernel, but all land on >>> the same page, kasan_early_shadow_page's content can be considered >>> garbage. When KASAN checks memory accesses for validity it detects >>> these garbage shadow values, but doesn't print any reports, as the >>> reporting routine bails out on the current->kasan_depth check (which >>> has the value of 1 initially). Only after kasan_init() completes, when >>> the proper shadow memory is mapped, current->kasan_depth gets set to 0 >>> and we start reporting bad accesses. >> >> That's surprising, because in the early phase I map the shadow area >> read-only, so I do not expect it to get modified unless RO protection is >> failing for some reason. > > Actually it might be that the allocator hooks don't modify shadow at > this point, as the allocator is not yet initialized. However stack > should be getting poisoned and unpoisoned from the very start. But the > generic statement that early shadow gets dirtied should be correct. > Might it be that you don't use stack instrumentation? > Yes, stack instrumentation is not used here, because shadow offset which we pass to the -fasan-shadow-offset= cflag is not specified here. So the logic in scrpits/Makefile.kasan just fallbacks to CFLAGS_KASAN_MINIMAL, which is outline and without stack instrumentation. Christophe, you can specify KASAN_SHADOW_OFFSET either in Kconfig (e.g. x86_64) or in Makefile (e.g. arm64). And make early mapping writable, because compiler generated code will write to shadow memory in function prologue/epilogue.