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.