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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7939DC433EF for ; Tue, 19 Apr 2022 06:35:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 13CC48D004D; Tue, 19 Apr 2022 02:35:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0C4DD8D0047; Tue, 19 Apr 2022 02:35:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EA8E18D004D; Tue, 19 Apr 2022 02:35:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.a.hostedemail.com [64.99.140.24]) by kanga.kvack.org (Postfix) with ESMTP id D5CBD8D0047 for ; Tue, 19 Apr 2022 02:35:44 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay12.hostedemail.com (Postfix) with ESMTP id 893B912076C for ; Tue, 19 Apr 2022 06:35:44 +0000 (UTC) X-FDA: 79372667808.23.B63AF7A Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by imf23.hostedemail.com (Postfix) with ESMTP id 7461614000B for ; Tue, 19 Apr 2022 06:35:42 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4KjDZY35rWzhY01; Tue, 19 Apr 2022 14:35:33 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 19 Apr 2022 14:35:39 +0800 Subject: Re: [PATCH] mm/madvise: fix potential pte_unmap_unlock pte error To: Andrew Morton CC: , , , , , References: <20220416081416.23304-1-linmiaohe@huawei.com> <20220418210951.b87743ae8b7c01f883e571ea@linux-foundation.org> From: Miaohe Lin Message-ID: <14389d75-bcc9-285a-f141-4de16fd34fac@huawei.com> Date: Tue, 19 Apr 2022 14:35:39 +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: <20220418210951.b87743ae8b7c01f883e571ea@linux-foundation.org> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 7461614000B X-Stat-Signature: 3u1fnpebgdck7nj1qet874h74tksek5r Authentication-Results: imf23.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf23.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-HE-Tag: 1650350142-147089 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 2022/4/19 12:09, Andrew Morton wrote: > On Sat, 16 Apr 2022 16:14:16 +0800 Miaohe Lin wrote: > >> We can't assume pte_offset_map_lock will return same orig_pte value. So >> it's necessary to reacquire the orig_pte or pte_unmap_unlock will unmap >> the stale pte. > > hm, where did you learn this info about pte_offset_map_lock()? > > I assume this is from code inspection only? No observed runtime failures? Yes, this is from code inspection. There is no observed runtime failures now due to the race window being really small. And this becomes noop in !CONFIG_HIGHMEM system (CONFIG_HIGHMEM system should be rare now). But this could be triggered theoretically. Thanks! > . >