From patchwork Fri Mar 4 09:34:08 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miaohe Lin X-Patchwork-Id: 12768819 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 6B2F8C433EF for ; Fri, 4 Mar 2022 09:35:35 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 158848D0012; Fri, 4 Mar 2022 04:35:15 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 104208D0005; Fri, 4 Mar 2022 04:35:15 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F0E358D0012; Fri, 4 Mar 2022 04:35:14 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.28]) by kanga.kvack.org (Postfix) with ESMTP id DF00A8D0005 for ; Fri, 4 Mar 2022 04:35:14 -0500 (EST) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id B29CA20D2D for ; Fri, 4 Mar 2022 09:35:14 +0000 (UTC) X-FDA: 79206195348.09.7FE0223 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by imf24.hostedemail.com (Postfix) with ESMTP id 0879618000D for ; Fri, 4 Mar 2022 09:35:13 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4K92hw4XcPzBrsy; Fri, 4 Mar 2022 17:33:20 +0800 (CST) Received: from huawei.com (10.175.124.27) 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 15.1.2308.21; Fri, 4 Mar 2022 17:35:10 +0800 From: Miaohe Lin To: CC: , , , , , , , , , , , , , , , , , , Subject: [PATCH 15/16] mm/migration: fix possible do_pages_stat_array racing with memory offline Date: Fri, 4 Mar 2022 17:34:08 +0800 Message-ID: <20220304093409.25829-16-linmiaohe@huawei.com> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20220304093409.25829-1-linmiaohe@huawei.com> References: <20220304093409.25829-1-linmiaohe@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.124.27] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: 0879618000D X-Stat-Signature: tiz1m5o65qz84jaj6w4yh1wytxtehqta X-Rspam-User: Authentication-Results: imf24.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf24.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.188 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Rspamd-Server: rspam03 X-HE-Tag: 1646386513-759489 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: When follow_page peeks a page, the page could be reclaimed under heavy memory pressure and thus be offlined while it's still being used by the do_pages_stat_array(). Use FOLL_GET to hold the page refcnt to fix this potential issue. Signed-off-by: Miaohe Lin --- mm/migrate.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index 7b1c0b988234..98a968e6f465 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1788,13 +1788,18 @@ static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, goto set_status; /* FOLL_DUMP to ignore special (like zero) pages */ - page = follow_page(vma, addr, FOLL_DUMP); + page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP); err = PTR_ERR(page); if (IS_ERR(page)) goto set_status; - err = page ? page_to_nid(page) : -ENOENT; + if (page) { + err = page_to_nid(page); + put_page(page); + } else { + err = -ENOENT; + } set_status: *status = err;