iommu/vt-d: Clear Present bit before tearing down scalable-mode context entry

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-74439
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-15 06:22:46 UTC
Updated2026-08-15 06:22:46 UTC
DescriptionIn 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.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 81e921fd321614c2ad8ac333b041aae1da7a1c6d e9e83bcfe37dc719182500dd823c03ab57d934f0 git Not specified
CNA Linux Linux affected 81e921fd321614c2ad8ac333b041aae1da7a1c6d 588718101e8449605f1c7e858fecb7cfa701cdab git Not specified
CNA Linux Linux affected 81e921fd321614c2ad8ac333b041aae1da7a1c6d 7fd4077dc92b91b1b844333c0a06bb9e286db10a git Not specified
CNA Linux Linux affected 81e921fd321614c2ad8ac333b041aae1da7a1c6d f46452c3df7a8d8a5addc0926e76ef19ea7da0a0 git Not specified
CNA Linux Linux affected 333fe86968482ca701c609af590003bcea450e8f git Not specified
CNA Linux Linux affected 6.8.2 6.9 semver Not specified
CNA Linux Linux affected 6.9 Not specified
CNA Linux Linux unaffected 6.9 semver Not specified
CNA Linux Linux unaffected 6.12.97 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.40 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.5 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/e9e83bcfe37dc719182500dd823c03ab57d934f0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/7fd4077dc92b91b1b844333c0a06bb9e286db10a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/588718101e8449605f1c7e858fecb7cfa701cdab 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f46452c3df7a8d8a5addc0926e76ef19ea7da0a0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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