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 F3FF6C433EF for ; Tue, 8 Mar 2022 11:47:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243626AbiCHLsY (ORCPT ); Tue, 8 Mar 2022 06:48:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45628 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1346566AbiCHLr7 (ORCPT ); Tue, 8 Mar 2022 06:47:59 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9EFF025EB9 for ; Tue, 8 Mar 2022 03:47:02 -0800 (PST) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4KCYMm3qgFzbcCB; Tue, 8 Mar 2022 19:42:12 +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 15.1.2308.21; Tue, 8 Mar 2022 19:46:59 +0800 Subject: Re: [PATCH 14/16] mm/migration: fix potential invalid node access for reclaim-based migration To: Baolin Wang , "Huang, Ying" CC: , , , , , , , , , , , , , , , , References: <20220304093409.25829-1-linmiaohe@huawei.com> <20220304093409.25829-15-linmiaohe@huawei.com> <87ee3e5opu.fsf@yhuang6-desk2.ccr.corp.intel.com> <0e74a360-6a72-4edf-47bb-8358a3f1d883@linux.alibaba.com> From: Miaohe Lin Message-ID: <64dc4cfa-96a9-f6a8-0575-223cc4c0f9d9@huawei.com> Date: Tue, 8 Mar 2022 19:46:59 +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: <0e74a360-6a72-4edf-47bb-8358a3f1d883@linux.alibaba.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.76] 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 On 2022/3/7 15:04, Baolin Wang wrote: > > > On 3/7/2022 1:14 PM, Huang, Ying wrote: >> Baolin Wang writes: >> >>> On 3/4/2022 5:34 PM, Miaohe Lin wrote: >>>> If we failed to setup hotplug state callbacks for mm/demotion:online in >>>> some corner cases, node_demotion will be left uninitialized. Invalid node >>>> might be returned from the next_demotion_node() when doing reclaim-based >>>> migration. Use kcalloc to allocate node_demotion to fix the issue. >>>> Fixes: ac16ec835314 ("mm: migrate: support multiple target nodes >>>> demotion") >>>> Signed-off-by: Miaohe Lin >>>> --- >>>>    mm/migrate.c | 6 +++--- >>>>    1 file changed, 3 insertions(+), 3 deletions(-) >>>> diff --git a/mm/migrate.c b/mm/migrate.c >>>> index 279940c0c064..7b1c0b988234 100644 >>>> --- a/mm/migrate.c >>>> +++ b/mm/migrate.c >>>> @@ -2516,9 +2516,9 @@ static int __init migrate_on_reclaim_init(void) >>>>    { >>>>        int ret; >>>>    -    node_demotion = kmalloc_array(nr_node_ids, >>>> -                      sizeof(struct demotion_nodes), >>>> -                      GFP_KERNEL); >>>> +    node_demotion = kcalloc(nr_node_ids, >>>> +                sizeof(struct demotion_nodes), >>>> +                GFP_KERNEL); >>> >>> Nit: not sure if this is worthy of this rare corner case, but I think >>> the target demotion nodes' default value should be NUMA_NO_NODE >>> instead of 0. >> >> The "nr" field of "struct demotion_nodes" should be initialized as 0.  I >> think that is checked before "nodes[]" field. > > Right, but it will be confusing that if nr = 0, while the nodes[] still contains valid node id 0. While we are at this, why not initialize the node_demotion structure with a clear default value? Anyway, no strong opinion on this :) IMO, this might not deserve initializing the node_demotion structure with a clear default value as cpuhp_setup_state fails at init time should be a rare case. Thanks both of you. > .