mm: memfd_luo: always dirty all folios

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Summary

CVECVE-2026-43389
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-08 15:16:50 UTC
Updated2026-05-12 14:10:27 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: mm: memfd_luo: always dirty all folios A dirty folio is one which has been written to. A clean folio is its opposite. Since a clean folio has no user data, it can be freed under memory pressure. memfd preservation with LUO saves the flag at preserve(). This is problematic. The folio might get dirtied later. Saving it at freeze() also doesn't work, since the dirty bit from PTE is normally synced at unmap and there might still be mappings of the file at freeze(). To see why this is a problem, say a folio is clean at preserve, but gets dirtied later. The serialized state of the folio will mark it as clean. After retrieve, the next kernel will see the folio as clean and might try to reclaim it under memory pressure. This will result in losing user data. Mark all folios of the file as dirty, and always set the MEMFD_LUO_FOLIO_DIRTY flag. This comes with the side effect of making all clean folios un-reclaimable. This is a cost that has to be paid for participants of live update. It is not expected to be a common use case to preserve a lot of clean folios anyway. Since the value of pfolio->flags is a constant now, drop the flags variable and set it directly.

Risk And Classification

EPSS: 0.000180000 probability, percentile 0.050780000 (date 2026-05-11)

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected b3749f174d686627f702234e64bad976dc432dbc e901c871d4b592f0042e30f3a0f031eae79744ec git Not specified
CNA Linux Linux affected b3749f174d686627f702234e64bad976dc432dbc 7e04bf1f33151a30e06a65b74b5f2c19fc2be128 git Not specified
CNA Linux Linux affected 6.19 Not specified
CNA Linux Linux unaffected 6.19 semver Not specified
CNA Linux Linux unaffected 6.19.9 6.19.* semver Not specified
CNA Linux Linux unaffected 7.0 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/7e04bf1f33151a30e06a65b74b5f2c19fc2be128 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e901c871d4b592f0042e30f3a0f031eae79744ec 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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