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 92F02C00140 for ; Tue, 2 Aug 2022 06:27:48 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C845C6B0071; Tue, 2 Aug 2022 02:27:47 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C33778E0001; Tue, 2 Aug 2022 02:27:47 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AD4CA6B0073; Tue, 2 Aug 2022 02:27:47 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 994A76B0071 for ; Tue, 2 Aug 2022 02:27:47 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 5A23DA1006 for ; Tue, 2 Aug 2022 06:27:47 +0000 (UTC) X-FDA: 79753671774.14.F8F097F Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by imf22.hostedemail.com (Postfix) with ESMTP id EF449C00D9 for ; Tue, 2 Aug 2022 06:27:44 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.54]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4LxlMS2cKmz1M8Sv; Tue, 2 Aug 2022 14:24:36 +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, 2 Aug 2022 14:27:36 +0800 Subject: Re: [bug report] mm, hwpoison: memory_failure races with alloc_fresh_huge_page/free_huge_page To: Muchun Song CC: Linux-MM , linux-kernel , Andrew Morton , Mike Kravetz , Naoya Horiguchi References: <3c542543-0965-ef60-4627-1a4116077a5b@huawei.com> From: Miaohe Lin Message-ID: Date: Tue, 2 Aug 2022 14:27:36 +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: 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 ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1659421667; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=uP1VCkil1vPqtfEc3ng3KdazHfz7HpDvCES/3ItiGZI=; b=6u9T5kz48uD/wT+6AknoCfOPcj6YEMV0CQ8Gn1+njE1KPLsUJplOrKvEyg0hfHBmGYJUFy 0jOLJ1qSlwpHQHsvmmEq81IYlworZ0eF2Hsaf5MHd4NUw/ObfIOfeJ8wkFJZLQoxNUQwgA 8Uul85kM3sK05SZ4Y2mqKmB6wmFqlcQ= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf22.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1659421667; a=rsa-sha256; cv=none; b=KRC4O4E6pm1q+co5DakCg3lQ8MRtRm2xC3UuGu2td2M6W9pZOqlIQAWYXewYxT9Kmfb5Fv btwR5OzhlmgU1PNX+QAERYBMA7le2h412FPuAruidwmEyeITSgO54k/JCC/63HNamHCsUh ZzDALH8NAjA1BMXouvNQfN0s8iKWWHs= X-Rspam-User: Authentication-Results: imf22.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf22.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Stat-Signature: jt1sfkdgyrdz3bnu1zgzta7r8d1g6sk7 X-Rspamd-Queue-Id: EF449C00D9 X-Rspamd-Server: rspam10 X-HE-Tag: 1659421664-313171 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 2022/8/2 12:07, Muchun Song wrote: > On Tue, Aug 02, 2022 at 10:00:50AM +0800, Miaohe Lin wrote: >> Hi all: >> When I investigate the mm/memory-failure.c code again, I found there's a possible race window >> between memory_failure and alloc_fresh_huge_page/free_huge_page. Thank about the below scene: >> >> CPU 1 CPU 2 >> alloc_fresh_huge_page -- page refcnt > 0 memory_failure >> prep_new_huge_page get_huge_page_for_hwpoison >> !PageHeadHuge -- so 2(not a hugepage) is returned >> hugetlb_vmemmap_optimize -- subpages is read-only >> set_compound_page_dtor -- PageHuge is true now, but too late!!! >> TestSetPageHWPoison(p) >> -- We might write to read-only subpages here!!! >> >> Another similar scene: >> >> CPU 1 CPU 2 >> free_huge_page -- page refcnt == 0 and not PageHuge memory_failure >> get_huge_page_for_hwpoison >> !PageHeadHuge -- so 2(not a hugepage) is returned >> TestSetPageHWPoison(p) >> -- We might write to read-only subpages here!!! >> hugetlb_vmemmap_restore -- subpages can be written to now, but too late!!! >> > > I agree this race is possible, I have proposed this race in thread [1]. Oh, I remember I see the race proposed in [1] but I did not look into that carefully at that time. Sorry. > But I didn't think more how to solve it. I hope this thread can find a good solution. :) > > [1] https://lore.kernel.org/linux-mm/20220623235153.2623702-1-naoya.horiguchi@linux.dev/T/#ma094a7cea7df8fd9a77a91551bf39077d89e23bd > >> I think the above scenes are possible. But I can't found a stable solution to fix it. Any suggestions? >> Or is it not worth to fix it as it's too rare? Or am I miss something? >> > > Luckily, the system will panic at once, which encountering this race. However, > we don't see any bug report. If we have an easy way to fix it, I think it is worth. Agree. But I can't find a easy way to fix it yet. > Just a quick reply, no suggestion/solutions from me. Many thanks for your quick reply. > > Thanks. > >> Any response would be appreciated! >> >> Thanks! >> > . >