CVE-2025-39961 - Vulnerability Details

Link	Providers
https://git.kernel.org/stable/c/075abf0b1a958acfbea2435003d228e738e90346
https://git.kernel.org/stable/c/1e56310b40fd2e7e0b9493da9ff488af145bdd0c
https://git.kernel.org/stable/c/7d462bdecb7d9c32934dab44aaeb7ea7d73a27a2
https://git.kernel.org/stable/c/cd92c8ab336c3a633d46e6f35ebcd3509ae7db3b

Type	Values Removed	Values Added
Description		In the Linux kernel, the following vulnerability has been resolved: iommu/amd/pgtbl: Fix possible race while increase page table level The AMD IOMMU host page table implementation supports dynamic page table levels (up to 6 levels), starting with a 3-level configuration that expands based on IOVA address. The kernel maintains a root pointer and current page table level to enable proper page table walks in alloc_pte()/fetch_pte() operations. The IOMMU IOVA allocator initially starts with 32-bit address and onces its exhuasted it switches to 64-bit address (max address is determined based on IOMMU and device DMA capability). To support larger IOVA, AMD IOMMU driver increases page table level. But in unmap path (iommu_v1_unmap_pages()), fetch_pte() reads pgtable->[root/mode] without lock. So its possible that in exteme corner case, when increase_address_space() is updating pgtable->[root/mode], fetch_pte() reads wrong page table level (pgtable->mode). It does compare the value with level encoded in page table and returns NULL. This will result is iommu_unmap ops to fail and upper layer may retry/log WARN_ON. CPU 0 CPU 1 ------ ------ map pages unmap pages alloc_pte() -> increase_address_space() iommu_v1_unmap_pages() -> fetch_pte() pgtable->root = pte (new root value) READ pgtable->[mode/root] Reads new root, old mode Updates mode (pgtable->mode += 1) Since Page table level updates are infrequent and already synchronized with a spinlock, implement seqcount to enable lock-free read operations on the read path.
Title		iommu/amd/pgtbl: Fix possible race while increase page table level
References		https://git.kernel.org/stable/c/075abf0b1a958acfbea2435003d228e738e90346 https://git.kernel.org/stable/c/1e56310b40fd2e7e0b9493da9ff488af145bdd0c https://git.kernel.org/stable/c/7d462bdecb7d9c32934dab44aaeb7ea7d73a27a2 https://git.kernel.org/stable/c/cd92c8ab336c3a633d46e6f35ebcd3509ae7db3b

{"dataType": "CVE_RECORD", "dataVersion": "5.1", "cveMetadata": {"cveId": "CVE-2025-39961", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2025-04-16T07:20:57.149Z", "datePublished": "2025-10-09T12:13:22.029Z", "dateUpdated": "2025-10-09T12:13:22.029Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2025-10-09T12:13:22.029Z"}, "descriptions": [{"lang": "en", "value": "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."}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["drivers/iommu/amd/amd_iommu_types.h", "drivers/iommu/amd/io_pgtable.c"], "versions": [{"version": "754265bcab78a9014f0f99cd35e0d610fcd7dfa7", "lessThan": "075abf0b1a958acfbea2435003d228e738e90346", "status": "affected", "versionType": "git"}, {"version": "754265bcab78a9014f0f99cd35e0d610fcd7dfa7", "lessThan": "cd92c8ab336c3a633d46e6f35ebcd3509ae7db3b", "status": "affected", "versionType": "git"}, {"version": "754265bcab78a9014f0f99cd35e0d610fcd7dfa7", "lessThan": "7d462bdecb7d9c32934dab44aaeb7ea7d73a27a2", "status": "affected", "versionType": "git"}, {"version": "754265bcab78a9014f0f99cd35e0d610fcd7dfa7", "lessThan": "1e56310b40fd2e7e0b9493da9ff488af145bdd0c", "status": "affected", "versionType": "git"}, {"version": "6fb92f18555a7b8e085267d513612dc0ff9a5360", "status": "affected", "versionType": "git"}, {"version": "b15bf74405faa1a65025eb8a6eb337e140e5250a", "status": "affected", "versionType": "git"}, {"version": "0d50f7b1e8c80a8c20db5049e269468c059b0378", "status": "affected", "versionType": "git"}, {"version": "785ca708a908b9c596ede852470ba28b8dc3e40b", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["drivers/iommu/amd/amd_iommu_types.h", "drivers/iommu/amd/io_pgtable.c"], "versions": [{"version": "5.3", "status": "affected"}, {"version": "0", "lessThan": "5.3", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.108", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.49", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.16.9", "lessThanOrEqual": "6.16.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.17", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.3", "versionEndExcluding": "6.6.108"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.3", "versionEndExcluding": "6.12.49"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.3", "versionEndExcluding": "6.16.9"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.3", "versionEndExcluding": "6.17"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.9.194"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.14.146"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19.75"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.2.17"}]}]}], "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"}}}}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "id": "CVE-2025-39961", "lastModified": "2025-10-09T13:15:32.250", "metrics": {}, "published": "2025-10-09T13:15:32.250", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/075abf0b1a958acfbea2435003d228e738e90346"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/1e56310b40fd2e7e0b9493da9ff488af145bdd0c"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/7d462bdecb7d9c32934dab44aaeb7ea7d73a27a2"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/cd92c8ab336c3a633d46e6f35ebcd3509ae7db3b"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

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