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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 A40CFC433E0 for ; Thu, 14 Jan 2021 02:52:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 58F7D23406 for ; Thu, 14 Jan 2021 02:52:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727095AbhANCwK (ORCPT ); Wed, 13 Jan 2021 21:52:10 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:11012 "EHLO szxga05-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725844AbhANCwI (ORCPT ); Wed, 13 Jan 2021 21:52:08 -0500 Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.60]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4DGTM52rSwzj7Sc; Thu, 14 Jan 2021 10:50:25 +0800 (CST) Received: from [10.174.176.197] (10.174.176.197) by DGGEMS413-HUB.china.huawei.com (10.3.19.213) with Microsoft SMTP Server id 14.3.498.0; Thu, 14 Jan 2021 10:51:24 +0800 Subject: Re: [PATCH] mm: Fix potential pte_unmap_unlock pte error To: Andi Kleen , Andrew Morton CC: , , , , References: <20210109080118.20885-1-linmiaohe@huawei.com> <20210110171443.GC1914459@tassilo.jf.intel.com> From: Miaohe Lin Message-ID: <530deddf-705e-045d-f7c6-521531dced71@huawei.com> Date: Thu, 14 Jan 2021 10:51:24 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <20210110171443.GC1914459@tassilo.jf.intel.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.176.197] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi: On 2021/1/11 1:14, Andi Kleen wrote: > On Sat, Jan 09, 2021 at 03:01:18AM -0500, Miaohe Lin wrote: >> Since commit 42e4089c7890 ("x86/speculation/l1tf: Disallow non privileged >> high MMIO PROT_NONE mappings"), when the first pfn modify is not allowed, >> we would break the loop with pte unchanged. Then the wrong pte - 1 would >> be passed to pte_unmap_unlock. > > Thanks. > > While the fix is correct, I'm not sure if it actually is a real bug. Is there > any architecture that would do something else than unlocking the underlying > page? If it's just the underlying page then it should be always the same > page, so no bug. > It's just a theoretical issue via code inspection. > That said of course the change is the right thing for main line, but probably doesn't > need to be backported. > So it should not be backported. Should I resend a patch or Andrew would kindly do this? > -Andi > . > Many thanks for review and reply.