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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 A428BC17441 for ; Mon, 11 Nov 2019 08:25:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 72F6A2084F for ; Mon, 11 Nov 2019 08:25:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 72F6A2084F 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 F32606B0005; Mon, 11 Nov 2019 03:25:13 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id EE31C6B0006; Mon, 11 Nov 2019 03:25:13 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id DF8C46B0007; Mon, 11 Nov 2019 03:25:13 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0066.hostedemail.com [216.40.44.66]) by kanga.kvack.org (Postfix) with ESMTP id C9FA66B0005 for ; Mon, 11 Nov 2019 03:25:13 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with SMTP id 96488180AD81A for ; Mon, 11 Nov 2019 08:25:13 +0000 (UTC) X-FDA: 76143311706.07.fuel40_67c197bb63c2a X-HE-Tag: fuel40_67c197bb63c2a X-Filterd-Recvd-Size: 3592 Received: from relay.sw.ru (relay.sw.ru [185.231.240.75]) by imf49.hostedemail.com (Postfix) with ESMTP for ; Mon, 11 Nov 2019 08:25:12 +0000 (UTC) Received: from [172.16.25.5] by relay.sw.ru with esmtp (Exim 4.92.3) (envelope-from ) id 1iU50L-00018h-TL; Mon, 11 Nov 2019 11:24:58 +0300 Subject: Re: [PATCH v3 1/2] kasan: detect negative size in memory operation function To: Dmitry Vyukov Cc: Walter Wu , Alexander Potapenko , Matthias Brugger , kasan-dev , Linux-MM , LKML , Linux ARM , wsd_upstream References: <20191104020519.27988-1-walter-zh.wu@mediatek.com> <34bf9c08-d2f2-a6c6-1dbe-29b1456d8284@virtuozzo.com> From: Andrey Ryabinin Message-ID: <20df03c5-e733-98b0-84e9-8d52ddce5c98@virtuozzo.com> Date: Mon, 11 Nov 2019 11:24:36 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 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 11/11/19 10:57 AM, Dmitry Vyukov wrote: > On Fri, Nov 8, 2019 at 11:32 PM Andrey Ryabinin wrote: >>> diff --git a/mm/kasan/generic_report.c b/mm/kasan/generic_report.c >>> index 36c645939bc9..52a92c7db697 100644 >>> --- a/mm/kasan/generic_report.c >>> +++ b/mm/kasan/generic_report.c >>> @@ -107,6 +107,24 @@ static const char *get_wild_bug_type(struct kasan_access_info *info) >>> >>> const char *get_bug_type(struct kasan_access_info *info) >>> { >>> + /* >>> + * If access_size is negative numbers, then it has three reasons >>> + * to be defined as heap-out-of-bounds bug type. >>> + * 1) Casting negative numbers to size_t would indeed turn up as >>> + * a large size_t and its value will be larger than ULONG_MAX/2, >>> + * so that this can qualify as out-of-bounds. >>> + * 2) If KASAN has new bug type and user-space passes negative size, >>> + * then there are duplicate reports. So don't produce new bug type >>> + * in order to prevent duplicate reports by some systems >>> + * (e.g. syzbot) to report the same bug twice. >>> + * 3) When size is negative numbers, it may be passed from user-space. >>> + * So we always print heap-out-of-bounds in order to prevent that >>> + * kernel-space and user-space have the same bug but have duplicate >>> + * reports. >>> + */ >> >> Completely fail to understand 2) and 3). 2) talks something about *NOT* producing new bug >> type, but at the same time you code actually does that. >> 3) says something about user-space which have nothing to do with kasan. > > The idea was to use one of the existing bug titles so that syzbot does > not produce 2 versions for OOBs where size is user-controlled. We > don't know if it's overflow from heap, global or stack, but heap is > the most common bug, so saying heap overflow will reduce chances of > producing duplicates the most. > But for all of this to work we do need to use one of the existing bug titles. The "heap-out-of-bounds" is not one of the existing bug titles.