Bug 2467189 (CVE-2026-43253)

Summary: CVE-2026-43253 kernel: iommu/amd: move wait_on_sem() out of spinlock
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's IOMMU (Input/Output Memory Management Unit) AMD component. When the system operates under a stressed environment with `iommu.strict=1` enabled, a busy-wait operation within the `wait_on_sem()` function can occur while holding a spinlock with interrupts disabled. This condition leads to increased contention and extended periods where the system cannot process interrupts, resulting in soft lockups. The primary consequence is a Denial of Service (DoS), making the system unresponsive.
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Description OSIDB Bzimport 2026-05-06 13:09:43 UTC 
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.
Comment 1 Keith Grant 2026-05-06 23:17:42 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026050604-CVE-2026-43253-838c@gregkh/T