CVE-2026-80718

In the Linux kernel, the following vulnerability has been resolved:

mm/percpu-km: fix bitmap overflow and accounting in pcpu_create_chunk()

In pcpu_create_chunk(), nr_pages is the total contiguous backing

allocation, i.e., nr_units * pcpu_unit_pages, but pcpu_chunk_populated()

uses it to set chunk->populated, whose size is pcpu_unit_pages, bitmap.

Since bit N in chunk->populated means page offset N inside every unit is

backed. When nr_units > 1, the function writes beyond chunk->populated.

Fix it by using chunk->nr_pages.

It also fixes the global pcpu_nr_empty_pop_pages accounting, since

pcpu_balance_free() only iterates up to chunk->nr_pages.

Commit a63d4ac4ab609 ("percpu: make percpu-km set chunk->populated bitmap

properly") introduced the bitmap overflow issue. Later, commit

b539b87fed37f ("percpu: implmeent pcpu_nr_empty_pop_pages and

chunk->nr_populated") added pcpu_nr_empty_pop_pages and caused the

accounting issue.