CVE-2026-93233 drm/nouveau/dmem: fix callocated underflow on large folio split
A local attacker can trigger an integer underflow in the nouveau driver, causing memory leaks and preventing resource reclamation, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-93233?
CVE-2026-93233 is a vulnerability in Linux, published on 24 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In 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.
Which versions are affected by CVE-2026-93233?
How do I fix CVE-2026-93233?
Apply the vendor's patch.
Is CVE-2026-93233 being exploited?
There is no known exploitation of CVE-2026-93233 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-93233, GHSA-xp29-rgmw-chx9, UBUNTU-CVE-2026-93233.