CVE-2026-68329

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

iommu/amd: Wait for completion instead of returning early in iommu_completion_wait()

need_sync is a per-IOMMU flag shared by all domains and devices behind

that IOMMU. It is set whenever a command is queued with sync == true and

cleared when a completion-wait (CWAIT) command is queued. However, a

cleared need_sync only means that a covering CWAIT has been queued, not

that all previously queued commands have actually completed in hardware.

iommu_completion_wait() read need_sync locklessly and returned early

when it was false. This breaks the "block until all previously queued

commands have completed" contract in a multi-CPU scenario:

CPU2: queue inv-B => need_sync = true

CPU1: queue CWAIT(N); need_sync = false; then wait_on_sem(N)

CPU2: read need_sync == false => return 0 (no wait!)

CPU2 returns without waiting for any sequence number even though its

inv-B may not have completed yet (CWA

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References