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=-0.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED 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 42803C31E57 for ; Mon, 17 Jun 2019 12:32:46 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1108A20644 for ; Mon, 17 Jun 2019 12:32:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Z6HQtWCe" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1108A20644 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=mediatek.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Date:To:From:Subject:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=JTcRKC7QMq1vdd2oZ7P2d7eg/UuXjMkhLO5VGl+QN3w=; b=Z6HQtWCedpNGNk /5qVry71pmNLBIl2d6SdPCOgiop+HMVkTPkuiMEGCDNEb8oNf3Np68783ogdiZfBw3n9xCVyxWxwr QwW3/nbQ7HjbNzNKNfvGF5AAMuYK67EDfo0LPRqiidCYMLphkYrL1NCBf5YiFYYVjGlIr29HnF+C+ FLbcdIcJLhtXsRtZ6/cA4ADgPacZ/9oWhBRvRImLS8JhH58L+Q5qrW9GRn91mGzAfltkiPYT8IzMo BV36KFAyfmTqd6Yyxqrj7cSvOmDXHGu8IoYq+cuLztNnGdStFbAQiB5AgJ3vtLKe73yaN51u/9DOk Inf91OSYZyWAtfJ3d9Vg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hcqoV-00032F-1w; Mon, 17 Jun 2019 12:32:43 +0000 Received: from mailgw01.mediatek.com ([216.200.240.184]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hcqoO-0002zG-TP; Mon, 17 Jun 2019 12:32:39 +0000 X-UUID: 447d37fa83d7467c96f4637d868145df-20190617 X-UUID: 447d37fa83d7467c96f4637d868145df-20190617 Received: from mtkcas68.mediatek.inc [(172.29.94.19)] by mailgw01.mediatek.com (envelope-from ) (musrelay.mediatek.com ESMTP with TLS) with ESMTP id 1978810227; Mon, 17 Jun 2019 04:32:29 -0800 Received: from mtkmbs08n2.mediatek.inc (172.21.101.56) by MTKMBS62N1.mediatek.inc (172.29.193.41) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Mon, 17 Jun 2019 05:32:28 -0700 Received: from mtkcas08.mediatek.inc (172.21.101.126) by mtkmbs08n2.mediatek.inc (172.21.101.56) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Mon, 17 Jun 2019 20:32:14 +0800 Received: from [172.21.84.99] (172.21.84.99) by mtkcas08.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Mon, 17 Jun 2019 20:32:14 +0800 Message-ID: <1560774735.15814.54.camel@mtksdccf07> Subject: Re: [PATCH v3] kasan: add memory corruption identification for software tag-based mode From: Walter Wu To: Dmitry Vyukov Date: Mon, 17 Jun 2019 20:32:15 +0800 In-Reply-To: References: <20190613081357.1360-1-walter-zh.wu@mediatek.com> <1560447999.15814.15.camel@mtksdccf07> <1560479520.15814.34.camel@mtksdccf07> <1560744017.15814.49.camel@mtksdccf07> X-Mailer: Evolution 3.2.3-0ubuntu6 MIME-Version: 1.0 X-TM-SNTS-SMTP: 792F3DD2252100ED132A309A0254155715B3B58D81E671EBE2156836FF5FF2582000:8 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190617_053236_966100_0E6FBF74 X-CRM114-Status: GOOD ( 27.48 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: wsd_upstream , "Jason A . Donenfeld" , Vasily Gorbik , Arnd Bergmann , Linux-MM , Andrey Konovalov , linux-mediatek@lists.infradead.org, LKML , kasan-dev , Pekka Enberg , Martin Schwidefsky , Miles Chen , Alexander Potapenko , David Rientjes , Matthias Brugger , Andrey Ryabinin , Christoph Lameter , Joonsoo Kim , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 2019-06-17 at 13:57 +0200, Dmitry Vyukov wrote: > On Mon, Jun 17, 2019 at 6:00 AM Walter Wu wrote: > > > > On Fri, 2019-06-14 at 10:32 +0800, Walter Wu wrote: > > > On Fri, 2019-06-14 at 01:46 +0800, Walter Wu wrote: > > > > On Thu, 2019-06-13 at 15:27 +0300, Andrey Ryabinin wrote: > > > > > > > > > > On 6/13/19 11:13 AM, Walter Wu wrote: > > > > > > This patch adds memory corruption identification at bug report for > > > > > > software tag-based mode, the report show whether it is "use-after-free" > > > > > > or "out-of-bound" error instead of "invalid-access" error.This will make > > > > > > it easier for programmers to see the memory corruption problem. > > > > > > > > > > > > Now we extend the quarantine to support both generic and tag-based kasan. > > > > > > For tag-based kasan, the quarantine stores only freed object information > > > > > > to check if an object is freed recently. When tag-based kasan reports an > > > > > > error, we can check if the tagged addr is in the quarantine and make a > > > > > > good guess if the object is more like "use-after-free" or "out-of-bound". > > > > > > > > > > > > > > > > > > > > > We already have all the information and don't need the quarantine to make such guess. > > > > > Basically if shadow of the first byte of object has the same tag as tag in pointer than it's out-of-bounds, > > > > > otherwise it's use-after-free. > > > > > > > > > > In pseudo-code it's something like this: > > > > > > > > > > u8 object_tag = *(u8 *)kasan_mem_to_shadow(nearest_object(cacche, page, access_addr)); > > > > > > > > > > if (access_addr_tag == object_tag && object_tag != KASAN_TAG_INVALID) > > > > > // out-of-bounds > > > > > else > > > > > // use-after-free > > > > > > > > Thanks your explanation. > > > > I see, we can use it to decide corruption type. > > > > But some use-after-free issues, it may not have accurate free-backtrace. > > > > Unfortunately in that situation, free-backtrace is the most important. > > > > please see below example > > > > > > > > In generic KASAN, it gets accurate free-backrace(ptr1). > > > > In tag-based KASAN, it gets wrong free-backtrace(ptr2). It will make > > > > programmer misjudge, so they may not believe tag-based KASAN. > > > > So We provide this patch, we hope tag-based KASAN bug report is the same > > > > accurate with generic KASAN. > > > > > > > > --- > > > > ptr1 = kmalloc(size, GFP_KERNEL); > > > > ptr1_free(ptr1); > > > > > > > > ptr2 = kmalloc(size, GFP_KERNEL); > > > > ptr2_free(ptr2); > > > > > > > > ptr1[size] = 'x'; //corruption here > > > > > > > > > > > > static noinline void ptr1_free(char* ptr) > > > > { > > > > kfree(ptr); > > > > } > > > > static noinline void ptr2_free(char* ptr) > > > > { > > > > kfree(ptr); > > > > } > > > > --- > > > > > > > We think of another question about deciding by that shadow of the first > > > byte. > > > In tag-based KASAN, it is immediately released after calling kfree(), so > > > the slub is easy to be used by another pointer, then it will change > > > shadow memory to the tag of new pointer, it will not be the > > > KASAN_TAG_INVALID, so there are many false negative cases, especially in > > > small size allocation. > > > > > > Our patch is to solve those problems. so please consider it, thanks. > > > > > Hi, Andrey and Dmitry, > > > > I am sorry to bother you. > > Would you tell me what you think about this patch? > > We want to use tag-based KASAN, so we hope its bug report is clear and > > correct as generic KASAN. > > > > Thanks your review. > > Walter > > Hi Walter, > > I will probably be busy till the next week. Sorry for delays. It's ok. Thanks your kindly help. I hope I can contribute to tag-based KASAN. It is a very important tool for us. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel