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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4410FC433EF for ; Fri, 4 Mar 2022 09:36:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238129AbiCDJhC (ORCPT ); Fri, 4 Mar 2022 04:37:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54014 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237652AbiCDJgD (ORCPT ); Fri, 4 Mar 2022 04:36:03 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 72C451903DB for ; Fri, 4 Mar 2022 01:35:13 -0800 (PST) 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 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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; -- 2.23.0