drm/nouveau/dmem: fix callocated underflow on large folio split

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Summary

CVECVE-2026-93233
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-24 16:17:18 UTC
Updated2026-09-24 16:17:18 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: drm/nouveau/dmem: fix callocated underflow on large folio split nouveau_dmem_folio_free() drops chunk->callocated once per freed folio, while a large (compound) device-private folio is only counted once when it is allocated. When such a folio is split, the mm core invokes ->folio_split() (nouveau_dmem_folio_split()) once for each new sub-folio, but the hook only fixes up the sub-folio metadata and leaves chunk->callocated unchanged. Each resulting sub-folio is later freed separately, so after a split the single allocation (+1) is met by N frees (-N), leaving chunk->callocated short by N-1. On the first split/free cycle it underflows: WARN_ON(!chunk->callocated) fires, the unsigned counter wraps and never returns to zero, so the chunk can no longer be reclaimed (nouveau_dmem_fini() also warns on the leaked count). Account for the new sub-folio in the split hook, under the same lock as nouveau_dmem_folio_free(), so the count stays balanced.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected c3228747107705d47c7e9a03598a434a0380cb73 0163b92946d0a7c816f619c57a4d9867954dd106 git Not specified
CNA Linux Linux affected c3228747107705d47c7e9a03598a434a0380cb73 c2256c044a1df39c8aad4dd2d6f709b2533e2d7a git Not specified
CNA Linux Linux affected 6.19 Not specified
CNA Linux Linux unaffected 6.19 semver Not specified
CNA Linux Linux unaffected 7.2.5 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/0163b92946d0a7c816f619c57a4d9867954dd106 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/c2256c044a1df39c8aad4dd2d6f709b2533e2d7a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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