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, MAILING_LIST_MULTI,SIGNED_OFF_BY,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 D36F3C4740C for ; Mon, 9 Sep 2019 13:07:49 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 80F3C20863 for ; Mon, 9 Sep 2019 13:07:49 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 80F3C20863 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id E7D786B0008; Mon, 9 Sep 2019 09:07:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id E2DA96B000A; Mon, 9 Sep 2019 09:07:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D1BFE6B000C; Mon, 9 Sep 2019 09:07:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0040.hostedemail.com [216.40.44.40]) by kanga.kvack.org (Postfix) with ESMTP id AA3F36B0008 for ; Mon, 9 Sep 2019 09:07:48 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 51C3A8243770 for ; Mon, 9 Sep 2019 13:07:48 +0000 (UTC) X-FDA: 75915409416.01.crib43_4417778514619 X-HE-Tag: crib43_4417778514619 X-Filterd-Recvd-Size: 4422 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf19.hostedemail.com (Postfix) with ESMTP for ; Mon, 9 Sep 2019 13:07:47 +0000 (UTC) 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 737C5ADDD; Mon, 9 Sep 2019 13:07:46 +0000 (UTC) Subject: Re: [PATCH v2 0/2] mm/kasan: dump alloc/free stack for page allocator To: walter-zh.wu@mediatek.com, Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Matthias Brugger , Andrew Morton , Martin Schwidefsky , Will Deacon , Andrey Konovalov , Arnd Bergmann , Thomas Gleixner , Michal Hocko , Qian Cai Cc: 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: <20190909082412.24356-1-walter-zh.wu@mediatek.com> From: Vlastimil Babka Message-ID: Date: Mon, 9 Sep 2019 15:07:45 +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: <20190909082412.24356-1-walter-zh.wu@mediatek.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit 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 9/9/19 10:24 AM, walter-zh.wu@mediatek.com wrote: > From: Walter Wu > > This patch is KASAN report adds the alloc/free stacks for page allocator > in order to help programmer to see memory corruption caused by page. > > By default, KASAN doesn't record alloc and free stack for page allocator. > It is difficult to fix up page use-after-free or dobule-free issue. > > Our patchsets will record the last stack of pages. > It is very helpful for solving the page use-after-free or double-free. > > KASAN report will show the last stack of page, it may be: > a) If page is in-use state, then it prints alloc stack. > It is useful to fix up page out-of-bound issue. I still disagree with duplicating most of page_owner functionality for the sake of using a single stack handle for both alloc and free (while page_owner + debug_pagealloc with patches in mmotm uses two handles). It reduces the amount of potentially important debugging information, and I really doubt the u32-per-page savings are significant, given the rest of KASAN overhead. > BUG: KASAN: slab-out-of-bounds in kmalloc_pagealloc_oob_right+0x88/0x90 > Write of size 1 at addr ffffffc0d64ea00a by task cat/115 > ... > Allocation stack of page: > set_page_stack.constprop.1+0x30/0xc8 > kasan_alloc_pages+0x18/0x38 > prep_new_page+0x5c/0x150 > get_page_from_freelist+0xb8c/0x17c8 > __alloc_pages_nodemask+0x1a0/0x11b0 > kmalloc_order+0x28/0x58 > kmalloc_order_trace+0x28/0xe0 > kmalloc_pagealloc_oob_right+0x2c/0x68 > > b) If page is freed state, then it prints free stack. > It is useful to fix up page use-after-free or double-free issue. > > BUG: KASAN: use-after-free in kmalloc_pagealloc_uaf+0x70/0x80 > Write of size 1 at addr ffffffc0d651c000 by task cat/115 > ... > Free stack of page: > kasan_free_pages+0x68/0x70 > __free_pages_ok+0x3c0/0x1328 > __free_pages+0x50/0x78 > kfree+0x1c4/0x250 > kmalloc_pagealloc_uaf+0x38/0x80 > > This has been discussed, please refer below link. > https://bugzilla.kernel.org/show_bug.cgi?id=203967 That's not a discussion, but a single comment from Dmitry, which btw contains "provide alloc *and* free stacks for it" ("it" refers to page, emphasis mine). It would be nice if he or other KASAN guys could clarify. > Changes since v1: > - slim page_owner and move it into kasan > - enable the feature by default > > Signed-off-by: Walter Wu > --- > include/linux/kasan.h | 1 + > lib/Kconfig.kasan | 2 ++ > mm/kasan/common.c | 32 ++++++++++++++++++++++++++++++++ > mm/kasan/kasan.h | 5 +++++ > mm/kasan/report.c | 27 +++++++++++++++++++++++++++ > 5 files changed, 67 insertions(+)