iommu/vt-d: Clear Present bit before tearing down PASID entry
- 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- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean?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 6.6.160, 6.12.75, 6.18.14, 6.19.4
- 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/vt-d: Clear Present bit before tearing down PASID entry The Intel VT-d Scalable Mode PASID table entry consists of 512 bits (64 bytes). When tearing down an entry, the current implementation zeros the entire 64-byte structure immediately using multiple 64-bit writes. Since the IOMMU hardware may fetch these 64 bytes using multiple internal transactions (e.g., four 128-bit bursts), updating or zeroing the entire entry while it is active (P=1) risks a "torn" read. If a hardware fetch occurs simultaneously with the CPU zeroing the entry, the hardware could observe an inconsistent state, leading to unpredictable behavior or spurious faults. Follow the "Guidance to Software for Invalidations" in the VT-d spec (Section 6.5.3.3) by implementing the recommended ownership handshake: 1. Clear only the 'Present' (P) bit of the PASID entry. 2. Use a dma_wmb() to ensure the cleared bit is visible to hardware before proceeding. 3. Execute the required invalidation sequence (PASID cache, IOTLB, and Device-TLB flush) to ensure the hardware has released all cached references. 4. Only after the flushes are complete, zero out the remaining fields of the PASID entry. Also, add a dma_wmb() in pasid_set_present() to ensure that all other fields of the PASID entry are visible to the hardware before the Present bit is set.
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: total
- Record last updated
Affected versions
- Linux Linux
From 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 · fixed in c36b0515c6445bd137ec8ad86ef5470c45d6e4bf; From 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 · fixed in a84d30e8d2bacd21782a6481158b7c9c552f4868; From 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 · fixed in 821807c167b7b48a41b95b6607c6b9f97600f7d9; From 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 · fixed in 949d71666e9dd19f21e7b4b53a88cd2c5b902858; From 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 · fixed in 75ed00055c059dedc47b5daaaa2f8a7a019138ff
- Linux Linux
5.0
- KernelLinux
From 5.0.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.75; From 6.13.0 · fixed in 6.18.14; From 6.19.0 · fixed in 6.19.4