---
id: CVE-2026-43253
title: 'iommu/amd: move wait_on_sem() out of spinlock'
summary: |-
  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(…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 4bf5beef578e46393f11eb69dda7d17a065e05ff <
    f2f65b28d802a667119147444ec2ae33eebf9a58
  - >-
    Linux >= 4bf5beef578e46393f11eb69dda7d17a065e05ff <
    715c263119fd1b918a9fcbd8a36ea5b604a46324
  - >-
    Linux >= 4bf5beef578e46393f11eb69dda7d17a065e05ff <
    e15768e68820142077bbca402d8e902f64ade1b0
  - >-
    Linux >= 4bf5beef578e46393f11eb69dda7d17a065e05ff <
    496269d12072ecb219826485bdbec70c92a8eef5
  - >-
    Linux >= 4bf5beef578e46393f11eb69dda7d17a065e05ff <
    d2a0cac10597068567d336e85fa3cbdbe8ca62bf
  - Linux 4.9
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-10-16T15:16:08.841212Z'
published: '2026-05-06'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:20:37.900Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-43253'
references:
  - url: 'https://git.kernel.org/stable/c/f2f65b28d802a667119147444ec2ae33eebf9a58'
  - url: 'https://git.kernel.org/stable/c/715c263119fd1b918a9fcbd8a36ea5b604a46324'
  - url: 'https://git.kernel.org/stable/c/e15768e68820142077bbca402d8e902f64ade1b0'
  - url: 'https://git.kernel.org/stable/c/496269d12072ecb219826485bdbec70c92a8eef5'
  - url: 'https://git.kernel.org/stable/c/d2a0cac10597068567d336e85fa3cbdbe8ca62bf'
tags:
  - cve.org
epss: 0.00486
epssPercentile: 0.40473
ingestedAt: '2026-10-16T17:24:46.690Z'
---

## Overview

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

- `Linux >= 4bf5beef578e46393f11eb69dda7d17a065e05ff < f2f65b28d802a667119147444ec2ae33eebf9a58`
- `Linux >= 4bf5beef578e46393f11eb69dda7d17a065e05ff < 715c263119fd1b918a9fcbd8a36ea5b604a46324`
- `Linux >= 4bf5beef578e46393f11eb69dda7d17a065e05ff < e15768e68820142077bbca402d8e902f64ade1b0`
- `Linux >= 4bf5beef578e46393f11eb69dda7d17a065e05ff < 496269d12072ecb219826485bdbec70c92a8eef5`
- `Linux >= 4bf5beef578e46393f11eb69dda7d17a065e05ff < d2a0cac10597068567d336e85fa3cbdbe8ca62bf`
- `Linux 4.9`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.