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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 4322EC54EAA for ; Fri, 27 Jan 2023 13:20:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=9jqBCG3lT2RHGD9G5HvR0kBlZzLAvVX/LPPT/5nLaKA=; b=tSl6oSYUQhu43R jqcoMkiwxYIQf8xl056j+kOSyxHMHsLPQjbV0XsNew9maSq9cAoS5U36TypmqMJ3uwysMMePLOqfB /YLxJfXhx5lpNAFP4JF1ynCjhSncL+VhhaUejJcqbu4evIKrXFSootD+djAWKObULBaviaQg6dSqg II2/yz5mOwaoq4JvVtRd0HVmGaK/H34j/FidLq5AO0qh0/jlDULMD9Tm5Enw90jSG+EigLMTvu7lY uPKp4f4sueU5HR3eBVZgkXUsHb7+4PpaozYOZLM3hBQ0LwXenjqhIrGKm4Mmy7hOvWkFKfdLbnnAG oUX5KhVw5hL5xRKZbdEw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pLOdU-00EwL0-Dg; Fri, 27 Jan 2023 13:19:21 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pLO4k-00EgMO-9Q for linux-arm-kernel@lists.infradead.org; Fri, 27 Jan 2023 12:43:27 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BB6642F; Fri, 27 Jan 2023 04:44:04 -0800 (PST) Received: from [10.57.88.221] (unknown [10.57.88.221]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 993FF3F5A1; Fri, 27 Jan 2023 04:43:21 -0800 (PST) Message-ID: Date: Fri, 27 Jan 2023 12:43:17 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Subject: Re: [PATCH V2] arm64/mm: Intercept pfn changes in set_pte_at() Content-Language: en-GB To: Will Deacon , Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, Mark Rutland , Andrew Morton , linux-kernel@vger.kernel.org, Mark Brown References: <20230109052816.405335-1-anshuman.khandual@arm.com> <20230126133321.GB29148@willie-the-truck> From: Robin Murphy In-Reply-To: <20230126133321.GB29148@willie-the-truck> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230127_044326_428106_BC1243E3 X-CRM114-Status: GOOD ( 17.11 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2023-01-26 13:33, Will Deacon wrote: > On Tue, Jan 24, 2023 at 11:11:49AM +0530, Anshuman Khandual wrote: >> On 1/9/23 10:58, Anshuman Khandual wrote: >>> Changing pfn on a user page table mapped entry, without first going through >>> break-before-make (BBM) procedure is unsafe. This just updates set_pte_at() >>> to intercept such changes, via an updated pgattr_change_is_safe(). This new >>> check happens via __check_racy_pte_update(), which has now been renamed as >>> __check_safe_pte_update(). >>> >>> Cc: Catalin Marinas >>> Cc: Will Deacon >>> Cc: Mark Rutland >>> Cc: Andrew Morton >>> Cc: linux-arm-kernel@lists.infradead.org >>> Cc: linux-kernel@vger.kernel.org >>> Signed-off-by: Anshuman Khandual >>> --- >>> This applies on v6.2-rc3. This patch had some test time on an internal CI >>> system without any issues being reported. >> >> Gentle ping, any updates on this patch ? Still any concerns ? > > I don't think we really got to the bottom of Mark's concerns with > unreachable ptes on the stack, did we? I also have vague recollections > of somebody (Robin?) running into issues with the vmap code not honouring > BBM. Doesn't ring a bell, so either it wasn't me, or it was many years ago and about 5 levels deep into trying to fix something else :/ > So I think we should confirm/fix the vmap issue before we enable this check > and also try to get some testing coverage to address Mark's worries. I think > he has a syzkaller instance set up, so that sound like a good place to > start. I think we're also missing a subtlety here in that this restriction doesn't *always* apply. For instance if someone wants to move a page by making the mapping read-only, copying the contents to a new page, then pointing the RO mapping at that new page, that should technically not require BBM. Thanks, Robin. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel