CVE-2026-45894iommu/vt-d: Clear Present bit before tearing down PASID entry
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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.
- CVSS
- 7.8 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Analyzed
- Record last updated
- Oct 16, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Linux Linux linux:linux (from the name) | from 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 before a84d30e8d2bacd21782a6481158b7c9c552f4868; from 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 before 821807c167b7b48a41b95b6607c6b9f97600f7d9; from 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 before 949d71666e9dd19f21e7b4b53a88cd2c5b902858; from 0bbeb01a4fafbf8422e5c8882d461d6ac4f71e15 before 75ed00055c059dedc47b5daaaa2f8a7a019138ff | CNA record |
linux linux_kernel linux:linux_kernel | from 5.0 before 6.12.75; from 6.13 before 6.18.14; from 6.19 before 6.19.4 | NVD |
References
- https://git.kernel.org/stable/c/a84d30e8d2bacd21782a6481158b7c9c552f4868patch
- https://git.kernel.org/stable/c/821807c167b7b48a41b95b6607c6b9f97600f7d9patch
- https://git.kernel.org/stable/c/949d71666e9dd19f21e7b4b53a88cd2c5b902858patch
- https://git.kernel.org/stable/c/75ed00055c059dedc47b5daaaa2f8a7a019138ffpatch
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.