iommu/amd/pgtbl: Fix possible race while increase page table level
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 4.10, 4.15, 4.20, 5.3, 6.6.108, and 2 more
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
- Exploitation: none
- Automatable: no
- Technical impact: total
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.
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: total
- Record last updated
Affected versions
- Linux Linux
From 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 · fixed in 075abf0b1a958acfbea2435003d228e738e90346; From 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 · fixed in cd92c8ab336c3a633d46e6f35ebcd3509ae7db3b; From 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 · fixed in 7d462bdecb7d9c32934dab44aaeb7ea7d73a27a2; From 754265bcab78a9014f0f99cd35e0d610fcd7dfa7 · fixed in 1e56310b40fd2e7e0b9493da9ff488af145bdd0c; From 4.9.194 · fixed in 4.10; From 4.14.146 · fixed in 4.15; From 4.19.75 · fixed in 4.20; From 5.2.17 · fixed in 5.3
- Linux Linux
5.3
- KernelLinux
From 5.3.0 · fixed in 6.6.108; From 6.7.0 · fixed in 6.12.49; From 6.13.0 · fixed in 6.16.9