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SubjectRe: [PATCH 14/16] mm/migration: fix potential invalid node access for reclaim-based migration
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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 <linmiaohe@huawei.com>
> ---
> 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.

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