Re: [PATCH v2] mm/mm_init: handle alloc_percpu failure in free_area_init_core_hotplug

[David Hildenbrand (Arm)]

On 7/2/26 00:16, Gregory Price wrote:
> We miss a failed allocation check for pgdat->per_cpu_nodestats, which
> results in a NULL deref when we offset into the per-cpu area.
> 
> Propagate -ENOMEM up the stack and leave per_cpu_nodestats pointing
> at boot_nodestats so a later online can retry the allocation.
> 
> hotadd_init_pgdat() returns NULL on failure, which __try_online_node()
> already maps to -ENOMEM.
> 
> On failure nothing needs to be unwound:
>   - the node is never marked online
>   - per_cpu_nodestats is left pointing at boot_nodestats
>   - __add_memory_resource() cleans up pending memblock resources
>   - later online attempts retry the per_cpu_nodestats allocation
> 
> Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
> Link: https://sashiko.dev/#/patchset/20260627202243.758289-1-gourry%40gourry.net
> Fixes: 75ef71840539 ("mm, vmstat: add infrastructure for per-node vmstats")
> Signed-off-by: Gregory Price <gourry@xxxxxxxxxx>
> ---

Acked-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>

-- 
Cheers,

David