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 BE36AC4345F for ; Wed, 1 May 2024 10:13:53 +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-Transfer-Encoding:Content-Type: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=SfTCKBohNsJg8xCJzZf8DHI2vd5Eh9XVzQWlcSscuoo=; b=PffyF2ttuGkAnj q2OaXhXWp24Iz/hHPykizf23jelyCsXIOHb2dghF4k86gxZqzlRluU37Rd3uj7CZYuIgZI2t8XnVF vk4DwobCkZNtzQVUelCyr8xa+A6K1J4eP61krAzKEMGSgYsbk9AApQNnyOmTbLLBjRCKqbC7p3TFA 24MlWN/KtBijTv9obiVkZE5HrWAB7ZzyTrwxdb7doUN8gytnvrMVEda0KpdtSEuQjr6MyPaYVrvZj y4OgUvtsUShexYTujsyVyH6kf6MK6i/8vVIV/yh5Nw8BCnupxusAAbT/NQkPkIVmFF0ZFBdCfq7gR EmYUXNpN/jiCfBhAAt2A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1s26y8-0000000942k-1S8d; Wed, 01 May 2024 10:13:44 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1s26y6-0000000942A-2NeK for linux-arm-kernel@lists.infradead.org; Wed, 01 May 2024 10:13:43 +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 49E292F4; Wed, 1 May 2024 03:14:07 -0700 (PDT) Received: from [10.57.65.146] (unknown [10.57.65.146]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id A2F2E3F793; Wed, 1 May 2024 03:13:39 -0700 (PDT) Message-ID: Date: Wed, 1 May 2024 11:13:38 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] arm64/mm: pmd_mkinvalid() must handle swap pmds Content-Language: en-GB To: Catalin Marinas Cc: Will Deacon , Mark Rutland , Anshuman Khandual , Andrew Morton , Zi Yan , "Aneesh Kumar K.V" , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20240430133138.732088-1-ryan.roberts@arm.com> <171449974870.639201.3165060270571039049.b4-ty@arm.com> From: Ryan Roberts In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240501_031342_751985_EF4F8283 X-CRM114-Status: GOOD ( 15.73 ) 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-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 01/05/2024 11:04, Catalin Marinas wrote: > On Wed, May 01, 2024 at 09:05:17AM +0100, Ryan Roberts wrote: >> On 30/04/2024 18:57, Catalin Marinas wrote: >>> On Tue, 30 Apr 2024 14:31:38 +0100, Ryan Roberts wrote: >>>> __split_huge_pmd_locked() can be called for a present THP, devmap or >>>> (non-present) migration entry. It calls pmdp_invalidate() >>>> unconditionally on the pmdp and only determines if it is present or not >>>> based on the returned old pmd. >>>> >>>> But arm64's pmd_mkinvalid(), called by pmdp_invalidate(), >>>> unconditionally sets the PMD_PRESENT_INVALID flag, which causes future >>>> pmd_present() calls to return true - even for a swap pmd. Therefore any >>>> lockless pgtable walker could see the migration entry pmd in this state >>>> and start interpretting the fields (e.g. pmd_pfn()) as if it were >>>> present, leading to BadThings (TM). GUP-fast appears to be one such >>>> lockless pgtable walker. >>>> >>>> [...] >>> >>> Applied to arm64 (for-next/fixes), thanks! It should land in 6.9-rc7. I >>> removed the debug/test code, please send it as a separate patch for >>> 6.10. >> >> Thanks Catalin! I'm guessing this will turn up in today's linux-next, so if I >> send the tests today and Andrew puts them straight in mm-unstable (which will >> goto linux-next) there is no risk that the tests are there without the fix? Or >> do I need to hold off until the fix is in v6.9-rc7? > > It looks like we don't push for-next/fixes to linux-next, it's > short-lived usually, it ends up upstream quickly. I can send the pull > request later today, should turn up in mainline by tomorrow. You can add > a note to your patch for Andrew that it will fail on arm64 until the fix > ends up upstream. It's a matter of a couple of days anyway. OK, I just didn't want to send it only for our CI to start failing. I'll do as you suggest. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel