[SRU][Q][PATCH 0/1] CVE-2026-31589

[Cengiz Can]

https://ubuntu.com/security/CVE-2026-31589

[ Impact ]

In folio_unmap_invalidate(), filemap_free_folio() could be called after the
folio had already been removed from the mapping, at a point where the code no
longer held a reference to or a lock on the mapping. Since the folio no longer
pinned the mapping, the mapping could be freed concurrently, leading to a use-
after-free when accessing mapping->a_ops. With a CVSS score of 9.8, this is
remotely exploitable and can lead to memory corruption or privilege escalation.

[ Fix ]

questing: backported with AI-assisted adaptation

[ Test Plan ]

Boot tested.

[ Where Problems Could Occur ]

A regression in this memory management change could affect folio invalidation
and the page cache writeback path, potentially causing incorrect free_folio()
callback handling or leaks. Any error here would manifest in core mm behavior
and could impact filesystem and I/O stability across the system.