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 CB79AC3A5A5 for ; Thu, 5 Sep 2019 08:03:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A5F17217D7 for ; Thu, 5 Sep 2019 08:03:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732155AbfIEIDc (ORCPT ); Thu, 5 Sep 2019 04:03:32 -0400 Received: from mx2.suse.de ([195.135.220.15]:50888 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1732004AbfIEIDb (ORCPT ); Thu, 5 Sep 2019 04:03:31 -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 CBEA8AD6B; Thu, 5 Sep 2019 08:03:28 +0000 (UTC) Subject: Re: [PATCH 1/2] mm/kasan: dump alloc/free stack for page allocator To: Walter Wu Cc: Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Matthias Brugger , Andrew Morton , Martin Schwidefsky , Arnd Bergmann , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com References: <20190904065133.20268-1-walter-zh.wu@mediatek.com> <401064ae-279d-bef3-a8d5-0fe155d0886d@suse.cz> <1567605965.32522.14.camel@mtksdccf07> <7998e8f1-e5e2-da84-ea1f-33e696015dce@suse.cz> <1567607063.32522.24.camel@mtksdccf07> From: Vlastimil Babka Openpgp: preference=signencrypt Autocrypt: addr=vbabka@suse.cz; prefer-encrypt=mutual; keydata= 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hFNGBTYyPq6mGW9jqaQ8en3ZmmJyw3CHwxZ5FZQ5qc55xgshKiy8jEtxh+dgB9d8zE/S/UGI E99N/q+kEKSgSMQMJ/CYPHQJVTi4YHh1yq/qTkHRX+ortrF5VEeDJDv+SljNStIxUdroPD29 2ijoaMFTAU+uBtE14UP5F+LWdmRdEGS1Ah1NwooL27uAFllTDQxDhg/+LJ/TqB8ZuidOIy1B xVKRSg3I2m+DUTVqBy7Lixo73hnW69kSjtqCeamY/NSu6LNP+b0wAOKhwz9hBEwEHLp05+mj 5ZFJyfGsOiNUcMoO/17FO4EBxSDP3FDLllpuzlFD7SXkfJaMWYmXIlO0jLzdfwfcnDzBbPwO hBM8hvtsyq8lq8vJOxv6XD6xcTtj5Az8t2JjdUX6SF9hxJpwhBU0wrCoGDkWp4Bbv6jnF7zP Nzftr4l8RuJoywDIiJpdaNpSlXKpj/K6KrnyAI/joYc7 Message-ID: <99913463-0e2c-7dab-c1eb-8b9e149b3ee3@suse.cz> Date: Thu, 5 Sep 2019 10:03:28 +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: <1567607063.32522.24.camel@mtksdccf07> Content-Type: text/plain; charset=utf-8 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 9/4/19 4:24 PM, Walter Wu wrote: > On Wed, 2019-09-04 at 16:13 +0200, Vlastimil Babka wrote: >> On 9/4/19 4:06 PM, Walter Wu wrote: >> >> The THP fix is not required for the rest of the series, it was even merged to >> mainline separately. >> >>> And It looks like something is different, because we only need last >>> stack of page, so it can decrease memory overhead. >> >> That would save you depot_stack_handle_t (which is u32) per page. I guess that's >> nothing compared to KASAN overhead? >> > If we can use less memory, we can achieve what we want. Why not? In my experience to solve some UAFs, it's important to know not only the freeing stack, but also the allocating stack. Do they make sense together, or not? In some cases, even longer history of alloc/free would be nice :) Also by simply recording the free stack in the existing depot handle, you might confuse existing page_owner file consumers, who won't know that this is a freeing stack. All that just doesn't seem to justify saving an u32 per page. > Thanks. > Walter > > >