CVE-2025-38447
mm/rmap: fix potential out-of-bounds page table access during batched unmap
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mm/rmap: fix potential out-of-bounds page table access during batched unmap
In the Linux kernel, the following vulnerability has been resolved: mm/rmap: fix potential out-of-bounds page table access during batched unmap As pointed out by David[1], the batched unmap logic in try_to_unmap_one() may read past the end of a PTE table when a large folio's PTE mappings are not fully contained within a single page table. While this scenario might be rare, an issue triggerable from userspace must be fixed regardless of its likelihood. This patch fixes the out-of-bounds access by refactoring the logic into a new helper, folio_unmap_pte_batch(). The new helper correctly calculates the safe batch size by capping the scan at both the VMA and PMD boundaries. To simplify the code, it also supports partial batching (i.e., any number of pages from 1 up to the calculated safe maximum), as there is no strong reason to special-case for fully mapped folios.
Reserved 2025-04-16 | Published 2025-07-25 | Updated 2025-07-25 | Assigner Linuxgit.kernel.org/...c/510fe9c15d07e765d96be9a9dc37e5057c6c09f4
git.kernel.org/...c/ddd05742b45b083975a0855ef6ebbf88cf1f532a
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