{"api_version":"1","generated_at":"2026-08-14T05:29:29+00:00","cve":"CVE-2025-39961","urls":{"html":"https://cve.report/CVE-2025-39961","api":"https://cve.report/api/cve/CVE-2025-39961.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2025-39961","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2025-39961"},"summary":{"title":"iommu/amd/pgtbl: Fix possible race while increase page table level","description":"In the Linux kernel, the following vulnerability has been resolved:\n\niommu/amd/pgtbl: Fix possible race while increase page table level\n\nThe AMD IOMMU host page table implementation supports dynamic page table levels\n(up to 6 levels), starting with a 3-level configuration that expands based on\nIOVA address. The kernel maintains a root pointer and current page table level\nto enable proper page table walks in alloc_pte()/fetch_pte() operations.\n\nThe IOMMU IOVA allocator initially starts with 32-bit address and onces its\nexhuasted it switches to 64-bit address (max address is determined based\non IOMMU and device DMA capability). To support larger IOVA, AMD IOMMU\ndriver increases page table level.\n\nBut in unmap path (iommu_v1_unmap_pages()), fetch_pte() reads\npgtable->[root/mode] without lock. So its possible that in exteme corner case,\nwhen increase_address_space() is updating pgtable->[root/mode], fetch_pte()\nreads wrong page table level (pgtable->mode). It does compare the value with\nlevel encoded in page table and returns NULL. This will result is\niommu_unmap ops to fail and upper layer may retry/log WARN_ON.\n\nCPU 0                                         CPU 1\n------                                       ------\nmap pages                                    unmap pages\nalloc_pte() -> increase_address_space()      iommu_v1_unmap_pages() -> fetch_pte()\n  pgtable->root = pte (new root value)\n                                             READ pgtable->[mode/root]\n\t\t\t\t\t       Reads new root, old mode\n  Updates mode (pgtable->mode += 1)\n\nSince Page table level updates are infrequent and already synchronized with a\nspinlock, implement seqcount to enable lock-free read operations on the read path.","state":"PUBLISHED","assigner":"Linux","published_at":"2025-10-09 13:15:32","updated_at":"2026-07-30 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Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2025-39961","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 075abf0b1a958acfbea2435003d228e738e90346 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 cd92c8ab336c3a633d46e6f35ebcd3509ae7db3b git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 7d462bdecb7d9c32934dab44aaeb7ea7d73a27a2 git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 1e56310b40fd2e7e0b9493da9ff488af145bdd0c git","platforms":[]},{"source":"CNA","vendor":"Linux","product":"Linux","version":"affected 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the Linux kernel, the following vulnerability has been resolved:\n\niommu/amd/pgtbl: Fix possible race while increase page table level\n\nThe AMD IOMMU host page table implementation supports dynamic page table levels\n(up to 6 levels), starting with a 3-level configuration that expands based on\nIOVA address. The kernel maintains a root pointer and current page table level\nto enable proper page table walks in alloc_pte()/fetch_pte() operations.\n\nThe IOMMU IOVA allocator initially starts with 32-bit address and onces its\nexhuasted it switches to 64-bit address (max address is determined based\non IOMMU and device DMA capability). To support larger IOVA, AMD IOMMU\ndriver increases page table level.\n\nBut in unmap path (iommu_v1_unmap_pages()), fetch_pte() reads\npgtable->[root/mode] without lock. So its possible that in exteme corner case,\nwhen increase_address_space() is updating pgtable->[root/mode], fetch_pte()\nreads wrong page table level (pgtable->mode). It does compare the value with\nlevel encoded in page table and returns NULL. This will result is\niommu_unmap ops to fail and upper layer may retry/log WARN_ON.\n\nCPU 0                                         CPU 1\n------                                       ------\nmap pages                                    unmap pages\nalloc_pte() -> increase_address_space()      iommu_v1_unmap_pages() -> fetch_pte()\n  pgtable->root = pte (new root value)\n                                             READ pgtable->[mode/root]\n\t\t\t\t\t       Reads new root, old mode\n  Updates mode (pgtable->mode += 1)\n\nSince Page table level updates are infrequent and already synchronized with a\nspinlock, implement seqcount to enable lock-free read operations on the read path."}],"metrics":[{"cvssV3_1":{"baseScore":8.8,"baseSeverity":"HIGH","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","version":"3.1"}}],"providerMetadata":{"dateUpdated":"2026-07-30T05:58:52.228Z","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux"},"references":[{"url":"https://git.kernel.org/stable/c/075abf0b1a958acfbea2435003d228e738e90346"},{"url":"https://git.kernel.org/stable/c/cd92c8ab336c3a633d46e6f35ebcd3509ae7db3b"},{"url":"https://git.kernel.org/stable/c/7d462bdecb7d9c32934dab44aaeb7ea7d73a27a2"},{"url":"https://git.kernel.org/stable/c/1e56310b40fd2e7e0b9493da9ff488af145bdd0c"}],"title":"iommu/amd/pgtbl: Fix possible race while increase page table level","x_generator":{"engine":"bippy-1.2.0"}}},"cveMetadata":{"assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","assignerShortName":"Linux","cveId":"CVE-2025-39961","datePublished":"2025-10-09T12:13:22.029Z","dateReserved":"2025-04-16T07:20:57.149Z","dateUpdated":"2026-07-30T05:58:52.228Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2025-10-09 13:15:32","lastModifiedDate":"2026-07-30 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Fix possible race while increase page table lev","CVE":"CVE-2025-39961","Year":"2025"},"notes":[{"CveYear":"2025","CveId":"39961","Ordinal":"1","NoteData":"In the Linux kernel, the following vulnerability has been resolved:\n\niommu/amd/pgtbl: Fix possible race while increase page table level\n\nThe AMD IOMMU host page table implementation supports dynamic page table levels\n(up to 6 levels), starting with a 3-level configuration that expands based on\nIOVA address. The kernel maintains a root pointer and current page table level\nto enable proper page table walks in alloc_pte()/fetch_pte() operations.\n\nThe IOMMU IOVA allocator initially starts with 32-bit address and onces its\nexhuasted it switches to 64-bit address (max address is determined based\non IOMMU and device DMA capability). To support larger IOVA, AMD IOMMU\ndriver increases page table level.\n\nBut in unmap path (iommu_v1_unmap_pages()), fetch_pte() reads\npgtable->[root/mode] without lock. So its possible that in exteme corner case,\nwhen increase_address_space() is updating pgtable->[root/mode], fetch_pte()\nreads wrong page table level (pgtable->mode). It does compare the value with\nlevel encoded in page table and returns NULL. This will result is\niommu_unmap ops to fail and upper layer may retry/log WARN_ON.\n\nCPU 0                                         CPU 1\n------                                       ------\nmap pages                                    unmap pages\nalloc_pte() -> increase_address_space()      iommu_v1_unmap_pages() -> fetch_pte()\n  pgtable->root = pte (new root value)\n                                             READ pgtable->[mode/root]\n\t\t\t\t\t       Reads new root, old mode\n  Updates mode (pgtable->mode += 1)\n\nSince Page table level updates are infrequent and already synchronized with a\nspinlock, implement seqcount to enable lock-free read operations on the read path.","Type":"Description","Title":"iommu/amd/pgtbl: Fix possible race while increase page table lev"}]}}}