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,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 E14F3C4741F for ; Thu, 5 Nov 2020 15:59:35 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 714C120936 for ; Thu, 5 Nov 2020 15:59:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="lXLDrLfX" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 714C120936 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+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=merlin.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:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ldpYU9mpMNA5tILAP936/pQsDj/K2b50xo4d1Ac2oBI=; b=lXLDrLfXeh3xIsce2ylXh7FkX cRuBzkKHXCVZ6iFxxSNOd7KmRGx9iWRkPlUrzoeo8ptfS3MqhnWS0S3PXUmsUYnnyXwgfP6H6rgpo jp88G5I1ysdaYHB1D8+33QUsLRb63QweqsSD7Bt1cDYyFURlygfRv/Wb+wCcdQK0xmgbTgAcgIPs/ QvRbNbpwCBPiuNCKjPhUG+DL8RN8qid211DAmkW8Twp05ezg4WEQwNmo2QxrBEwVm2IEqZPLjt6tt TaBZAg6zMITHhILv64LIDTRnDgwVuyDd6VsQUQ77R9vSjURKUsygm6GLG29dWxZj8abwAUOurnxZ9 rhzht6hMQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kahfK-0000uc-6P; Thu, 05 Nov 2020 15:59:10 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kahfH-0000ts-RH for linux-arm-kernel@lists.infradead.org; Thu, 05 Nov 2020 15:59:08 +0000 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 637012087D; Thu, 5 Nov 2020 15:59:03 +0000 (UTC) Date: Thu, 5 Nov 2020 15:59:00 +0000 From: Catalin Marinas To: Andrey Konovalov Subject: Re: [PATCH v8 28/43] arm64: mte: Reset the page tag in page->flags Message-ID: <20201105155859.GA30030@gaia> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201105_105908_005433_0BC26BC9 X-CRM114-Status: GOOD ( 18.00 ) 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: linux-arm-kernel@lists.infradead.org, Marco Elver , Kevin Brodsky , Will Deacon , Branislav Rankov , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Alexander Potapenko , Evgenii Stepanov , Andrey Ryabinin , Andrew Morton , Vincenzo Frascino , Dmitry Vyukov Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Nov 05, 2020 at 12:18:43AM +0100, Andrey Konovalov wrote: > diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c > index 8f99c65837fd..06ba6c923ab7 100644 > --- a/arch/arm64/kernel/mte.c > +++ b/arch/arm64/kernel/mte.c > @@ -34,6 +34,7 @@ static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap) > return; > } > > + page_kasan_tag_reset(page); > mte_clear_page_tags(page_address(page)); I think we need an smp_wmb() between setting the flags and clearing the actual tags. If another threads reads page->flags and builds a tagged address out of it (see page_to_virt) there's an address dependency to the actual memory access. However, on the current thread, we don't guarantee that the new page->flags are visible before the tags were updated. > } > > diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c > index 70a71f38b6a9..348f4627da08 100644 > --- a/arch/arm64/mm/copypage.c > +++ b/arch/arm64/mm/copypage.c > @@ -22,6 +22,7 @@ void copy_highpage(struct page *to, struct page *from) > copy_page(kto, kfrom); > > if (system_supports_mte() && test_bit(PG_mte_tagged, &from->flags)) { > + page_kasan_tag_reset(to); > set_bit(PG_mte_tagged, &to->flags); > mte_copy_page_tags(kto, kfrom); Nitpick: move page_kasan_tag_reset() just above mte_copy_page_tags() for consistency with the other places where PG_mte_tagged is set before or after the actual tag setting. > } > diff --git a/arch/arm64/mm/mteswap.c b/arch/arm64/mm/mteswap.c > index c52c1847079c..0e7eccbe598a 100644 > --- a/arch/arm64/mm/mteswap.c > +++ b/arch/arm64/mm/mteswap.c > @@ -53,6 +53,7 @@ bool mte_restore_tags(swp_entry_t entry, struct page *page) > if (!tags) > return false; > > + page_kasan_tag_reset(page); > mte_restore_page_tags(page_address(page), tags); There is another mte_restore_page_tags() caller in hibernate.c. That one doesn't need page_kasan_tag_reset() since the page->flags would have been already restored but please add a comment in that file why its not needed. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel