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=-5.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 74526C4CEC5 for ; Thu, 12 Sep 2019 17:05:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 52AF22081B for ; Thu, 12 Sep 2019 17:05:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731247AbfILRFb (ORCPT ); Thu, 12 Sep 2019 13:05:31 -0400 Received: from relay.sw.ru ([185.231.240.75]:49202 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728091AbfILRFb (ORCPT ); Thu, 12 Sep 2019 13:05:31 -0400 Received: from [172.16.25.5] by relay.sw.ru with esmtp (Exim 4.92) (envelope-from ) id 1i8SWx-0001JP-U8; Thu, 12 Sep 2019 20:05:16 +0300 Subject: Re: [PATCH v3] mm/kasan: dump alloc and free stack for page allocator To: Vlastimil Babka , Walter Wu Cc: Qian Cai , Alexander Potapenko , Dmitry Vyukov , Matthias Brugger , Andrew Morton , Martin Schwidefsky , Andrey Konovalov , Arnd Bergmann , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com References: <20190911083921.4158-1-walter-zh.wu@mediatek.com> <5E358F4B-552C-4542-9655-E01C7B754F14@lca.pw> <1568297308.19040.5.camel@mtksdccf07> <613f9f23-c7f0-871f-fe13-930c35ef3105@suse.cz> From: Andrey Ryabinin Message-ID: <79fede05-735b-8477-c273-f34db93fd72b@virtuozzo.com> Date: Thu, 12 Sep 2019 20:05:14 +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: <613f9f23-c7f0-871f-fe13-930c35ef3105@suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/12/19 5:31 PM, Vlastimil Babka wrote: > On 9/12/19 4:08 PM, Walter Wu wrote: >> >>>   extern void __reset_page_owner(struct page *page, unsigned int order); >>> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan >>> index 6c9682ce0254..dc560c7562e8 100644 >>> --- a/lib/Kconfig.kasan >>> +++ b/lib/Kconfig.kasan >>> @@ -41,6 +41,8 @@ config KASAN_GENERIC >>>       select SLUB_DEBUG if SLUB >>>       select CONSTRUCTORS >>>       select STACKDEPOT >>> +    select PAGE_OWNER >>> +    select PAGE_OWNER_FREE_STACK >>>       help >>>         Enables generic KASAN mode. >>>         Supported in both GCC and Clang. With GCC it requires version 4.9.2 >>> @@ -63,6 +65,8 @@ config KASAN_SW_TAGS >>>       select SLUB_DEBUG if SLUB >>>       select CONSTRUCTORS >>>       select STACKDEPOT >>> +    select PAGE_OWNER >>> +    select PAGE_OWNER_FREE_STACK >>>       help >> >> What is the difference between PAGE_OWNER+PAGE_OWNER_FREE_STACK and >> DEBUG_PAGEALLOC? > > Same memory usage, but debug_pagealloc means also extra checks and restricting memory access to freed pages to catch UAF. > >> If you directly enable PAGE_OWNER+PAGE_OWNER_FREE_STACK >> PAGE_OWNER_FREE_STACK,don't you think low-memory device to want to use >> KASAN? > > OK, so it should be optional? But I think it's enough to distinguish no PAGE_OWNER at all, and PAGE_OWNER+PAGE_OWNER_FREE_STACK together - I don't see much point in PAGE_OWNER only for this kind of debugging. > > So how about this? KASAN wouldn't select PAGE_OWNER* but it would be recommended in the help+docs. When PAGE_OWNER and KASAN are selected by user, PAGE_OWNER_FREE_STACK gets also selected, and both will be also runtime enabled without explicit page_owner=on. > I mostly want to avoid another boot-time option for enabling PAGE_OWNER_FREE_STACK. > Would that be enough flexibility for low-memory devices vs full-fledged debugging? Originally I thought that with you patch users still can disable page_owner via "page_owner=off" boot param. But now I realized that this won't work. I think it should work, we should allow users to disable it. Or another alternative option (and actually easier one to implement), leave PAGE_OWNER as is (no "select"s in Kconfigs) Make PAGE_OWNER_FREE_STACK like this: +config PAGE_OWNER_FREE_STACK + def_bool KASAN || DEBUG_PAGEALLOC + depends on PAGE_OWNER + So, users that want alloc/free stack will have to enable CONFIG_PAGE_OWNER=y and add page_owner=on to boot cmdline. Basically the difference between these alternative is whether we enable page_owner by default or not. But there is always a possibility to disable it.