CVE-2026-64031 in Linux
Résumé
par MITRE • 19/07/2026
In the Linux kernel, the following vulnerability has been resolved:
erofs: fix managed cache race for unaligned extents
After unaligned compressed extents were introduced, the following race could occur:
[Thread 1] [Thread 2]
(z_erofs_fill_bio_vec) <handle a Z_EROFS_PREALLOCATED_FOLIO folio> ... filemap_add_folio (1) (z_erofs_bind_cache) <the same folio is found..> .. .. folio_attach_private (2) filemap_add_folio (3) again
Since (1) is executed but (2) hasn't been executed yet, it's possible that another thread finds the same managed folio in z_erofs_bind_cache() for a different pcluster and calls filemap_add_folio() again since folio->private is still Z_EROFS_PREALLOCATED_FOLIO.
Fix this by explicitly clearing folio->private before making the folio visible in the managed cache so that another pcluster can simply wait on the locked managed folio as what we did for other shared cases [1].
This only impacts unaligned data compression (`-E48bit` with zstd, for example).
[1] Commit 9e2f9d34dd12 ("erofs: handle overlapped pclusters out of
crafted images properly") was originally introduced to handle crafted overlapped extents, but it addresses unaligned extents as well.
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