{"id":"AZL-76434","summary":"CVE-2025-39961 affecting package kernel 5.15.200.1-1","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":"2026-04-01T05:22:57.381684Z","published":"2025-10-09T13:15:32Z","upstream":["CVE-2025-39961"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2025-39961"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:2","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"5.15.200.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-76434.json"}}],"schema_version":"1.7.5"}