---
id: CVE-2026-80633
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  iommufd: Take dma_resv lock before dma_buf_unpin() in release path

  dma_buf_unpin() requires the caller to hold the exporter's dma_resv
  lock:

    void dma_buf_unpin(stru…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  iommufd: Take dma_resv lock before dma_buf_unpin() in release path

  dma_buf_unpin() requires the caller to hold the exporter's dma_resv
  lock:

    void dma_buf_unpin(stru…
severity: high
cvss: 8.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H'
published: '2026-08-28'
updated: '2026-08-29'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-80633'
references:
  - url: 'https://git.kernel.org/stable/c/cc69d0332421fd2943b66dbe5e597bf4fd5af126'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/e745cd2c749e557c14a15ac931761c3f58c24489'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
epss: 0.00165
epssPercentile: 0.05026
ingestedAt: '2026-08-30T03:46:31.010Z'
---

## Overview

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

iommufd: Take dma_resv lock before dma_buf_unpin() in release path

dma_buf_unpin() requires the caller to hold the exporter's dma_resv
lock:

  void dma_buf_unpin(struct dma_buf_attachment *attach)
  {
          ...
          dma_resv_assert_held(dmabuf->resv);
          ...
  }

iopt_release_pages() calls dma_buf_unpin() without taking that lock,
so every iommufd_ioas_destroy()/iommufd_ioas_unmap() that releases
the last reference on a DMABUF-backed iopt_pages triggers a WARN.
This was hit while running tools/testing/selftests/iommu/iommufd:

  WARNING: drivers/dma-buf/dma-buf.c:1137 at dma_buf_unpin+0x62/0x70
  RIP: 0010:dma_buf_unpin+0x62/0x70
  Call Trace:
   <TASK>
   dma_buf_unpin+0x62/0x70
   iopt_release_pages+0xe4/0x190
   iopt_unmap_iova_range+0x1c7/0x290
   iopt_unmap_all+0x1a/0x30
   iommufd_ioas_destroy+0x1d/0x50
   iommufd_fops_release+0x93/0x150
   __fput+0xfc/0x2c0
   __x64_sys_close+0x3d/0x80
   do_syscall_64+0x65/0x180
   </TASK>

Take the dma_resv lock around dma_buf_unpin() in iopt_release_pages(),
matching the iopt_map_dmabuf() convention. dma_buf_detach() acquires the
reservation lock internally, so it must remain outside the locked region.

## Remediation

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