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=-8.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 17921C55ABD for ; Sat, 14 Nov 2020 12:43:55 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9ADFF22226 for ; Sat, 14 Nov 2020 12:43:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9ADFF22226 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id AC33A6B005C; Sat, 14 Nov 2020 07:43:53 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A73DF6B005D; Sat, 14 Nov 2020 07:43:53 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 98A046B0068; Sat, 14 Nov 2020 07:43:53 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0195.hostedemail.com [216.40.44.195]) by kanga.kvack.org (Postfix) with ESMTP id 687876B005C for ; Sat, 14 Nov 2020 07:43:53 -0500 (EST) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 093E98249980 for ; Sat, 14 Nov 2020 12:43:53 +0000 (UTC) X-FDA: 77482990746.03.car37_500199a27317 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin03.hostedemail.com (Postfix) with ESMTP id DCC0428A4E8 for ; Sat, 14 Nov 2020 12:43:52 +0000 (UTC) X-HE-Tag: car37_500199a27317 X-Filterd-Recvd-Size: 2603 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf23.hostedemail.com (Postfix) with ESMTP for ; Sat, 14 Nov 2020 12:43:52 +0000 (UTC) Received: from gaia (unknown [2.26.170.190]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1FFF720759; Sat, 14 Nov 2020 12:43:48 +0000 (UTC) Date: Sat, 14 Nov 2020 12:43:46 +0000 From: Catalin Marinas To: Andrey Konovalov Cc: Andrew Morton , Will Deacon , Vincenzo Frascino , Dmitry Vyukov , Andrey Ryabinin , Alexander Potapenko , Marco Elver , Evgenii Stepanov , Branislav Rankov , Kevin Brodsky , kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH mm v10 26/42] arm64: mte: Reset the page tag in page->flags Message-ID: <20201114124346.GC2837@gaia> References: <18bca1ff61bf6605289e7213153b3fd5b8f81e27.1605305705.git.andreyknvl@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <18bca1ff61bf6605289e7213153b3fd5b8f81e27.1605305705.git.andreyknvl@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Fri, Nov 13, 2020 at 11:15:54PM +0100, Andrey Konovalov wrote: > From: Vincenzo Frascino > > The hardware tag-based KASAN for compatibility with the other modes > stores the tag associated to a page in page->flags. > Due to this the kernel faults on access when it allocates a page with an > initial tag and the user changes the tags. > > Reset the tag associated by the kernel to a page in all the meaningful > places to prevent kernel faults on access. > > Note: An alternative to this approach could be to modify page_to_virt(). > This though could end up being racy, in fact if a CPU checks the > PG_mte_tagged bit and decides that the page is not tagged but another > CPU maps the same with PROT_MTE and becomes tagged the subsequent kernel > access would fail. > > Signed-off-by: Vincenzo Frascino > Signed-off-by: Andrey Konovalov Reviewed-by: Catalin Marinas