CVE-2025-39961 (GCVE-0-2025-39961)
Vulnerability from cvelistv5
Published
2025-10-09 12:13
Modified
2025-10-09 12:13
Severity ?
VLAI Severity ?
EPSS score ?
Summary
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.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 Version: 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 Version: 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 Version: 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 Version: 6fb92f18555a7b8e085267d513612dc0ff9a5360 Version: b15bf74405faa1a65025eb8a6eb337e140e5250a Version: 0d50f7b1e8c80a8c20db5049e269468c059b0378 Version: 785ca708a908b9c596ede852470ba28b8dc3e40b |
||
{
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"descriptions": [
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"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-\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."
}
],
"providerMetadata": {
"dateUpdated": "2025-10-09T12:13:22.029Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
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"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",
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"cveId": "CVE-2025-39961",
"datePublished": "2025-10-09T12:13:22.029Z",
"dateReserved": "2025-04-16T07:20:57.149Z",
"dateUpdated": "2025-10-09T12:13:22.029Z",
"state": "PUBLISHED"
},
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"vulnerability-lookup:meta": {
"nvd": "{\"cve\":{\"id\":\"CVE-2025-39961\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-10-09T13:15:32.250\",\"lastModified\":\"2025-10-09T15:50:04.013\",\"vulnStatus\":\"Awaiting Analysis\",\"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-\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.\"}],\"metrics\":{},\"references\":[{\"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\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
}
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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