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 6CA15C4CEC5 for ; Thu, 12 Sep 2019 14:31:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4943E20830 for ; Thu, 12 Sep 2019 14:31:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732694AbfILObp (ORCPT ); Thu, 12 Sep 2019 10:31:45 -0400 Received: from mx2.suse.de ([195.135.220.15]:40906 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1732579AbfILObo (ORCPT ); Thu, 12 Sep 2019 10:31:44 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id F35A4AFFE; Thu, 12 Sep 2019 14:31:42 +0000 (UTC) Subject: Re: [PATCH v3] mm/kasan: dump alloc and free stack for page allocator To: Walter Wu Cc: Qian Cai , Andrey Ryabinin , 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> From: Vlastimil Babka Message-ID: <613f9f23-c7f0-871f-fe13-930c35ef3105@suse.cz> Date: Thu, 12 Sep 2019 16:31:42 +0200 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: <1568297308.19040.5.camel@mtksdccf07> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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?