iommu/vt-d: Clear Present bit before tearing down scalable-mode context 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- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean?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 6.9, 6.12.97, 6.18.40, 7.1.5
- 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 scalable-mode context entry device_pasid_table_teardown() zeroes the 128-bit scalable-mode context entry with context_clear_entry() while the Present bit is still set. This creates a window where the hardware can fetch a torn entry, with some fields already zeroed while Present is still set, leading to unpredictable behavior or spurious faults. The context-cache invalidation is issued only after the entry has been zeroed, and intel_pasid_free_table() then frees the PASID directory pages, so the IOMMU can keep walking a stale Present=1 entry that points at freed memory. While x86 provides strong write ordering, the compiler may reorder the two 64-bit writes to the entry, and the hardware fetch is not guaranteed to be atomic with respect to multiple CPU writes. Commit c1e4f1dccbe9d ("iommu/vt-d: Clear Present bit before tearing down context entry") fixed this exact pattern in domain_context_clear_one() and the copied-context path, but device_pasid_table_teardown() was not converted. Align it with the "Guidance to Software for Invalidations" in the VT-d spec, Section 6.5.3.3, using the same ownership handshake as the sibling fix: clear only the Present bit, flush it to the IOMMU, perform the context-cache invalidation, and only then zero the rest of the entry.
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: total
- Record last updated
Affected versions
- Linux Linux
From 81e921fd321614c2ad8ac333b041aae1da7a1c6d · fixed in e9e83bcfe37dc719182500dd823c03ab57d934f0; From 81e921fd321614c2ad8ac333b041aae1da7a1c6d · fixed in 588718101e8449605f1c7e858fecb7cfa701cdab; From 81e921fd321614c2ad8ac333b041aae1da7a1c6d · fixed in 7fd4077dc92b91b1b844333c0a06bb9e286db10a; From 81e921fd321614c2ad8ac333b041aae1da7a1c6d · fixed in f46452c3df7a8d8a5addc0926e76ef19ea7da0a0; From 6.8.2 · fixed in 6.9
- Linux Linux
6.9
- KernelLinux
From 6.9.0 · fixed in 6.12.97; From 6.13.0 · fixed in 6.18.40; From 6.19.0 · fixed in 7.1.5