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 0F36BC433F5 for ; Tue, 8 Mar 2022 11:47:05 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 977248D0002; Tue, 8 Mar 2022 06:47:04 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 9260E8D0001; Tue, 8 Mar 2022 06:47:04 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8166C8D0002; Tue, 8 Mar 2022 06:47:04 -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 6F11C8D0001 for ; Tue, 8 Mar 2022 06:47:04 -0500 (EST) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay11.hostedemail.com (Postfix) with ESMTP id 439D4819A8 for ; Tue, 8 Mar 2022 11:47:04 +0000 (UTC) X-FDA: 79221042768.14.2216FE4 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by imf04.hostedemail.com (Postfix) with ESMTP id 34F994000F for ; Tue, 8 Mar 2022 11:47:03 +0000 (UTC) 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 X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 34F994000F X-Stat-Signature: ukd6ma6i6q6z1n1py7faenm59dgdxru9 Authentication-Results: imf04.hostedemail.com; dkim=none; dmarc=pass (policy=quarantine) header.from=huawei.com; spf=pass (imf04.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.187 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com X-Rspam-User: X-HE-Tag: 1646740023-211134 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 2022/3/7 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. > .