{"id":"CVE-2025-39961","title":"iommu/amd/pgtbl: Fix possible race while increase page table level","summary":"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), st…","severity":"high","cvss":8.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 < 075abf0b1a958acfbea2435003d228e738e90346","Linux >= 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 < cd92c8ab336c3a633d46e6f35ebcd3509ae7db3b","Linux >= 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 < 7d462bdecb7d9c32934dab44aaeb7ea7d73a27a2","Linux >= 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 < 1e56310b40fd2e7e0b9493da9ff488af145bdd0c","Linux 6fb92f18555a7b8e085267d513612dc0ff9a5360","Linux b15bf74405faa1a65025eb8a6eb337e140e5250a","Linux 0d50f7b1e8c80a8c20db5049e269468c059b0378","Linux 785ca708a908b9c596ede852470ba28b8dc3e40b","Linux >= 4.9.194 < 4.10","Linux >= 4.14.146 < 4.15","Linux >= 4.19.75 < 4.20","Linux >= 5.2.17 < 5.3","Linux 5.3"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-15T21:55:10.295299Z"},"published":"2025-10-09","updated":"2026-10-15","sourceUpdated":"2026-10-15T22:02:34.065Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2025-39961","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"}],"tags":["cve.org"],"epss":0.00115,"epssPercentile":0.01533,"ingestedAt":"2026-10-15T22:48:25.532Z","slug":"CVE-2025-39961","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `Linux >= 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 < 075abf0b1a958acfbea2435003d228e738e90346`\n- `Linux >= 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 < cd92c8ab336c3a633d46e6f35ebcd3509ae7db3b`\n- `Linux >= 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 < 7d462bdecb7d9c32934dab44aaeb7ea7d73a27a2`\n- `Linux >= 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 < 1e56310b40fd2e7e0b9493da9ff488af145bdd0c`\n- `Linux 6fb92f18555a7b8e085267d513612dc0ff9a5360`\n- `Linux b15bf74405faa1a65025eb8a6eb337e140e5250a`\n- `Linux 0d50f7b1e8c80a8c20db5049e269468c059b0378`\n- `Linux 785ca708a908b9c596ede852470ba28b8dc3e40b`\n- `Linux >= 4.9.194 < 4.10`\n- `Linux >= 4.14.146 < 4.15`\n- `Linux >= 4.19.75 < 4.20`\n- `Linux >= 5.2.17 < 5.3`\n- `Linux 5.3`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":48,"depthScoreParts":{"impact":48.4,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}