{"id":"CVE-2026-93233","state":"PUBLISHED","title":"drm/nouveau/dmem: fix callocated underflow on large folio split","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/nouveau/dmem: fix callocated underflow on large folio split\n\nnouveau_dmem_folio_free() drops chunk->callocated once per freed folio,\nwhile a large (compound) device-private folio is only counted once when\nit is allocated.  When such a folio is split, the mm core invokes\n->folio_split() (nouveau_dmem_folio_split()) once for each new\nsub-folio, but the hook only fixes up the sub-folio metadata and leaves\nchunk->callocated unchanged.\n\nEach resulting sub-folio is later freed separately, so after a split\nthe single allocation (+1) is met by N frees (-N), leaving\nchunk->callocated short by N-1.  On the first split/free cycle it\nunderflows: WARN_ON(!chunk->callocated) fires, the unsigned counter\nwraps and never returns to zero, so the chunk can no longer be\nreclaimed (nouveau_dmem_fini() also warns on the leaked count).\n\nAccount for the new sub-folio in the split hook, under the same lock as\nnouveau_dmem_folio_free(), so the count stays balanced.","publishedAt":"2026-09-24T15:32:51.743Z","updatedAt":"2026-10-19T09:07:44.949Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"c3228747107705d47c7e9a03598a434a0380cb73","status":"affected","lessThan":"0163b92946d0a7c816f619c57a4d9867954dd106","versionType":"git"},{"version":"c3228747107705d47c7e9a03598a434a0380cb73","status":"affected","lessThan":"c2256c044a1df39c8aad4dd2d6f709b2533e2d7a","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/nouveau/nouveau_dmem.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.19","versionType":"semver"},{"version":"7.2.5","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/nouveau/nouveau_dmem.c"]}],"references":["https://git.kernel.org/stable/c/0163b92946d0a7c816f619c57a4d9867954dd106","https://git.kernel.org/stable/c/c2256c044a1df39c8aad4dd2d6f709b2533e2d7a"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:34.582Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/93xxx/CVE-2026-93233.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-93233","state":"PUBLISHED","datePublished":"2026-09-24T15:32:51.743Z","dateUpdated":"2026-10-19T09:07:44.949Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-17T16:02:15.095Z"},"containers":{"cna":{"title":"drm/nouveau/dmem: fix callocated underflow on large folio split","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/nouveau/dmem: fix callocated underflow on large folio split\n\nnouveau_dmem_folio_free() drops chunk->callocated once per freed folio,\nwhile a large (compound) device-private folio is only counted once when\nit is allocated.  When such a folio is split, the mm core invokes\n->folio_split() (nouveau_dmem_folio_split()) once for each new\nsub-folio, but the hook only fixes up the sub-folio metadata and leaves\nchunk->callocated unchanged.\n\nEach resulting sub-folio is later freed separately, so after a split\nthe single allocation (+1) is met by N frees (-N), leaving\nchunk->callocated short by N-1.  On the first split/free cycle it\nunderflows: WARN_ON(!chunk->callocated) fires, the unsigned counter\nwraps and never returns to zero, so the chunk can no longer be\nreclaimed (nouveau_dmem_fini() also warns on the leaked count).\n\nAccount for the new sub-folio in the split hook, under the same lock as\nnouveau_dmem_folio_free(), so the count stays balanced."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"c3228747107705d47c7e9a03598a434a0380cb73","status":"affected","lessThan":"0163b92946d0a7c816f619c57a4d9867954dd106","versionType":"git"},{"version":"c3228747107705d47c7e9a03598a434a0380cb73","status":"affected","lessThan":"c2256c044a1df39c8aad4dd2d6f709b2533e2d7a","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/nouveau/nouveau_dmem.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.19","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.19","versionType":"semver"},{"version":"7.2.5","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["drivers/gpu/drm/nouveau/nouveau_dmem.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/0163b92946d0a7c816f619c57a4d9867954dd106"},{"url":"https://git.kernel.org/stable/c/c2256c044a1df39c8aad4dd2d6f709b2533e2d7a"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:07:44.949Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19","versionEndExcluding":"7.2.5"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}