# CVE-2021-47140: iommu/amd: Clear DMA ops when switching domain

> A local attacker with sysfs access can trigger a kernel null pointer dereference and crash the system by switching IOMMU domains on AMD hardware.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Mar 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47140, GHSA-vr5f-v75p-g4qw, UBUNTU-CVE-2021-47140

## What is CVE-2021-47140?

CVE-2021-47140 is a medium-severity vulnerability in Linux kernel, published on 25 Mar 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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

iommu/amd: Clear DMA ops when switching domain

Since commit 08a27c1c3ecf ("iommu: Add support to change default domain
of an iommu group") a user can switch a device between IOMMU and direct
DMA through sysfs. This doesn't work for AMD IOMMU at the moment because
dev->dma_ops is not cleared when switching from a DMA to an identity
IOMMU domain. The DMA layer thus attempts to use the dma-iommu ops on an
identity domain, causing an oops:

  # echo 0000:00:05.0 > /sys/sys/bus/pci/drivers/e1000e/unbind
  # echo identity > /sys/bus/pci/devices/0000:00:05.0/iommu_group/type
  # echo 0000:00:05.0 > /sys/sys/bus/pci/drivers/e1000e/bind
   ...
  BUG: kernel NULL pointer dereference, address: 0000000000000028
   ...
   Call Trace:
    iommu_dma_alloc
    e1000e_setup_tx_resources
    e1000e_open

Since iommu_change_dev_def_domain() calls probe_finalize() again, clear
the dma_ops there like Vt-d does.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2021-47140?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47140?

Apply the vendor's patch.

## Is CVE-2021-47140 being exploited?

There is no known exploitation of CVE-2021-47140 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-47140 and fix it if it is affected.

What it is: CVE-2021-47140 is a medium-severity vulnerability in Linux kernel, published on 25 Mar 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-47140 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2021-47140/ (Markdown: https://insights.sbomify.com/CVE-2021-47140/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47140
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47140
- OSV: https://osv.dev/vulnerability/CVE-2021-47140

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47140/
Summaries are generated and may contain mistakes; the official description above is the record.