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 98DEBC433F5 for ; Mon, 7 Mar 2022 07:04:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235588AbiCGHEx (ORCPT ); Mon, 7 Mar 2022 02:04:53 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37552 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230121AbiCGHEv (ORCPT ); Mon, 7 Mar 2022 02:04:51 -0500 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D73765A084 for ; Sun, 6 Mar 2022 23:03:56 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01424;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=20;SR=0;TI=SMTPD_---0V6QeAlb_1646636630; Received: from 30.97.48.83(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0V6QeAlb_1646636630) by smtp.aliyun-inc.com(127.0.0.1); Mon, 07 Mar 2022 15:03:51 +0800 Message-ID: <0e74a360-6a72-4edf-47bb-8358a3f1d883@linux.alibaba.com> Date: Mon, 7 Mar 2022 15:04:52 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [PATCH 14/16] mm/migration: fix potential invalid node access for reclaim-based migration To: "Huang, Ying" Cc: Miaohe Lin , akpm@linux-foundation.org, mike.kravetz@oracle.com, shy828301@gmail.com, willy@infradead.org, ziy@nvidia.com, minchan@kernel.org, apopple@nvidia.com, ave.hansen@linux.intel.com, o451686892@gmail.com, almasrymina@google.com, jhubbard@nvidia.com, rcampbell@nvidia.com, peterx@redhat.com, naoya.horiguchi@nec.com, mhocko@suse.com, riel@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20220304093409.25829-1-linmiaohe@huawei.com> <20220304093409.25829-15-linmiaohe@huawei.com> <87ee3e5opu.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Baolin Wang In-Reply-To: <87ee3e5opu.fsf@yhuang6-desk2.ccr.corp.intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 :)