CVE-2026-43253: iommu/amd: move wait_on_sem() out of spinlock

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-06 · updated 2026-10-30
Weakness: CWE-667

Description

In the Linux kernel, the following vulnerability has been resolved: iommu/amd: move wait_on_sem() out of spinlock With iommu.strict=1, the existing completion wait path can cause soft lockups under stressed environment, as wait_on_sem() busy-waits under the spinlock with interrupts disabled. Move the completion wait in iommu_completion_wait() out of the spinlock. wait_on_sem() only polls the hardware-updated cmd_sem and does not require iommu->lock, so holding the lock during the busy wait unnecessarily increases contention and extends the time with interrupts disabled.

Affected products

Linux kernel: from 4.9 before 6.6.128; from 6.7 before 6.12.75; from 6.13 before 6.18.16; from 6.19 before 6.19.6 — fixed in 6.6.128, 6.12.75, 6.18.16, 6.19.6
Linux: 4.9 — fixed in 7.0

How to fix

Upgrade to a fixed version: Linux kernel 6.6.128, 6.12.75, 6.18.16, 6.19.6; Linux 7.0. Check the vendor advisory for mitigations.

References

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