Description (CNA)
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.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 before 075abf0b1a958acfbea2435003d228e738e90346; affected 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 before cd92c8ab336c3a633d46e6f35ebcd3509ae7db3b; affected 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 before 7d462bdecb7d9c32934dab44aaeb7ea7d73a27a2; affected 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 before 1e56310b40fd2e7e0b9493da9ff488af145bdd0c; affected 6fb92f18555a7b8e085267d513612dc0ff9a5360; affected b15bf74405faa1a65025eb8a6eb337e140e5250a; affected 0d50f7b1e8c80a8c20db5049e269468c059b0378; affected 785ca708a908b9c596ede852470ba28b8dc3e40b; affected 4.9.194 before 4.10; affected 4.14.146 before 4.15; affected 4.19.75 before 4.20; affected 5.2.17 before 5.3 |
| Linux / Linux | affected 5.3; unaffected 0 before 5.3; unaffected 6.6.108 through 6.6.*; unaffected 6.12.49 through 6.12.*; unaffected 6.16.9 through 6.16.*; unaffected 6.17 through * |
CWE
No CWE identifiers supplied.
References
- https://git.kernel.org/stable/c/075abf0b1a958acfbea2435003d228e738e90346
- https://git.kernel.org/stable/c/cd92c8ab336c3a633d46e6f35ebcd3509ae7db3b
- https://git.kernel.org/stable/c/7d462bdecb7d9c32934dab44aaeb7ea7d73a27a2
- https://git.kernel.org/stable/c/1e56310b40fd2e7e0b9493da9ff488af145bdd0c
ADP enrichment
No English description supplied.
No references supplied.