{"id":"CVE-2025-39961","summary":"iommu/amd/pgtbl: Fix possible race while increase page table level","details":"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-\u003e[root/mode] without lock. So its possible that in exteme corner case,\nwhen increase_address_space() is updating pgtable-\u003e[root/mode], fetch_pte()\nreads wrong page table level (pgtable-\u003emode). 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() -\u003e increase_address_space()      iommu_v1_unmap_pages() -\u003e fetch_pte()\n  pgtable-\u003eroot = pte (new root value)\n                                             READ pgtable-\u003e[mode/root]\n\t\t\t\t\t       Reads new root, old mode\n  Updates mode (pgtable-\u003emode += 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.","modified":"2026-04-16T00:02:25.342896734Z","published":"2025-10-09T12:13:22.029Z","related":["SUSE-SU-2026:20012-1","SUSE-SU-2026:20015-1","SUSE-SU-2026:20021-1","openSUSE-SU-2025:20172-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39961.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/075abf0b1a958acfbea2435003d228e738e90346"},{"type":"WEB","url":"https://git.kernel.org/stable/c/1e56310b40fd2e7e0b9493da9ff488af145bdd0c"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7d462bdecb7d9c32934dab44aaeb7ea7d73a27a2"},{"type":"WEB","url":"https://git.kernel.org/stable/c/cd92c8ab336c3a633d46e6f35ebcd3509ae7db3b"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39961.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-39961"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"754265bcab78a9014f0f99cd35e0d610fcd7dfa7"},{"fixed":"075abf0b1a958acfbea2435003d228e738e90346"},{"fixed":"cd92c8ab336c3a633d46e6f35ebcd3509ae7db3b"},{"fixed":"7d462bdecb7d9c32934dab44aaeb7ea7d73a27a2"},{"fixed":"1e56310b40fd2e7e0b9493da9ff488af145bdd0c"}]},{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"0"},{"last_affected":"6fb92f18555a7b8e085267d513612dc0ff9a5360"},{"last_affected":"b15bf74405faa1a65025eb8a6eb337e140e5250a"},{"last_affected":"0d50f7b1e8c80a8c20db5049e269468c059b0378"},{"last_affected":"785ca708a908b9c596ede852470ba28b8dc3e40b"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2025-39961.json"}}],"schema_version":"1.7.5"}