linux-kernel - Re: [PATCH 14/16] mm/migration: fix potential invalid node access for reclaim-based migration

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Message-ID: <87a6e25ooy.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Mon, 07 Mar 2022 13:14:37 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     <akpm@...ux-foundation.org>, <mike.kravetz@...cle.com>,
        <shy828301@...il.com>, <willy@...radead.org>, <ziy@...dia.com>,
        <minchan@...nel.org>, <apopple@...dia.com>,
        <ave.hansen@...ux.intel.com>, <o451686892@...il.com>,
        <almasrymina@...gle.com>, <jhubbard@...dia.com>,
        <rcampbell@...dia.com>, <peterx@...hat.com>,
        <naoya.horiguchi@....com>, <mhocko@...e.com>, <riel@...hat.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 14/16] mm/migration: fix potential invalid node access
 for reclaim-based migration

Miaohe Lin <linmiaohe@...wei.com> writes:

> 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 <linmiaohe@...wei.com>

LGTM!  Thanks!

Reviewed-by: "Huang, Ying" <ying.huang@...el.com>

Best Regards,
Huang, Ying

> ---
>  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);
>  	WARN_ON(!node_demotion);
>  
>  	ret = cpuhp_setup_state_nocalls(CPUHP_MM_DEMOTION_DEAD, "mm/demotion:offline",