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=-5.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 6DE93C3A5A0 for ; Mon, 19 Aug 2019 14:07:11 +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 3E9D1206C1 for ; Mon, 19 Aug 2019 14:07:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="fHfbVqHF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3E9D1206C1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=virtuozzo.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:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=yI7Ik7zsVn342ssshQZnCcBjdZViFqaiRSG1KnZndr4=; b=fHfbVqHFLILMU7 NQBuMUmWVNbPHDVMJd0jEkXY2tkd6LF1NXyIAAEK13qGv8mCKmISzyU+Fo1x8wWle/Yg489kYV0+M s8X0XofZueai818g3pKvprmjkn73WZstK4seOLw5UFvzG8WFRKG1ITIMC3VRRkLfuGw2VYQCbyAkq q0xxaiwt6y+8WEb0G7O1+jBWJXvI0vjQele3bFLdyAaPNkterOWQnpBxtui3KfTcphAEu4skQ4FOC CY/FQhTnRecPhCy6lvgRQ38WBI2BD6qAKXie7pj4OKwt8UgQNWyy1thH3dnd78uI0iAqL+n8wSBdb Dmx/MQjoBM683gdiuTVQ==; 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 1hziJS-0000sD-JB; Mon, 19 Aug 2019 14:07:10 +0000 Received: from relay.sw.ru ([185.231.240.75]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hziIt-0008Qx-UM; Mon, 19 Aug 2019 14:06:39 +0000 Received: from [172.16.25.5] by relay.sw.ru with esmtp (Exim 4.92) (envelope-from ) id 1hziIi-0001H7-Gd; Mon, 19 Aug 2019 17:06:24 +0300 Subject: Re: [PATCH] arm64: kasan: fix phys_to_virt() false positive on tag-based kasan To: Will Deacon , Mark Rutland References: <20190819114420.2535-1-walter-zh.wu@mediatek.com> <20190819125625.bu3nbrldg7te5kwc@willie-the-truck> <20190819132347.GB9927@lakrids.cambridge.arm.com> <20190819133441.ejomv6cprdcz7hh6@willie-the-truck> From: Andrey Ryabinin Message-ID: <8df7ec20-2fd2-8076-9a34-ac4c9785e91a@virtuozzo.com> Date: Mon, 19 Aug 2019 17:06:33 +0300 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: <20190819133441.ejomv6cprdcz7hh6@willie-the-truck> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190819_070636_054582_28626A80 X-CRM114-Status: GOOD ( 19.46 ) 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: Walter Wu , wsd_upstream@mediatek.com, Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, Alexander Potapenko , linux-arm-kernel@lists.infradead.org, Andrey Konovalov , Matthias Brugger , linux-mediatek@lists.infradead.org, Andrew Morton , Dmitry Vyukov 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 8/19/19 4:34 PM, Will Deacon wrote: > On Mon, Aug 19, 2019 at 02:23:48PM +0100, Mark Rutland wrote: >> On Mon, Aug 19, 2019 at 01:56:26PM +0100, Will Deacon wrote: >>> On Mon, Aug 19, 2019 at 07:44:20PM +0800, Walter Wu wrote: >>>> __arm_v7s_unmap() call iopte_deref() to translate pyh_to_virt address, >>>> but it will modify pointer tag into 0xff, so there is a false positive. >>>> >>>> When enable tag-based kasan, phys_to_virt() function need to rewrite >>>> its original pointer tag in order to avoid kasan report an incorrect >>>> memory corruption. >>> >>> Hmm. Which tree did you see this on? We've recently queued a load of fixes >>> in this area, but I /thought/ they were only needed after the support for >>> 52-bit virtual addressing in the kernel. >> >> I'm seeing similar issues in the virtio blk code (splat below), atop of >> the arm64 for-next/core branch. I think this is a latent issue, and >> people are only just starting to test with KASAN_SW_TAGS. >> >> It looks like the virtio blk code will round-trip a SLUB-allocated pointer from >> virt->page->virt, losing the per-object tag in the process. >> >> Our page_to_virt() seems to get a per-page tag, but this only makes >> sense if you're dealing with the page allocator, rather than something >> like SLUB which carves a page into smaller objects giving each object a >> distinct tag. >> >> Any round-trip of a pointer from SLUB is going to lose the per-object >> tag. > > Urgh, I wonder how this is supposed to work? > We supposed to ignore pointers with 0xff tags. We do ignore them when memory access checked, but not in kfree() path. This untested patch should fix the issue: --- mm/kasan/common.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/kasan/common.c b/mm/kasan/common.c index 895dc5e2b3d5..0a81cc328049 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -407,7 +407,7 @@ static inline bool shadow_invalid(u8 tag, s8 shadow_byte) return shadow_byte < 0 || shadow_byte >= KASAN_SHADOW_SCALE_SIZE; else - return tag != (u8)shadow_byte; + return (tag != KASAN_TAG_KERNEL) && (tag != (u8)shadow_byte); } static bool __kasan_slab_free(struct kmem_cache *cache, void *object, -- 2.21.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel