# CVE-2021-47549: sata_fsl: fix UAF in sata_fsl_port_stop when rmmod sata_fsl

> A use-after-free vulnerability in the Linux kernel's sata_fsl driver allows a local attacker to cause a system crash by unloading the module.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 May 2024
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2021-47549, UBUNTU-CVE-2021-47549

## What is CVE-2021-47549?

CVE-2021-47549 is a high-severity use after free vulnerability in Linux kernel, published on 24 May 2024. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

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

sata_fsl: fix UAF in sata_fsl_port_stop when rmmod sata_fsl

When the `rmmod sata_fsl.ko` command is executed in the PPC64 GNU/Linux,
a bug is reported:
 ==================================================================
 BUG: Unable to handle kernel data access on read at 0x80000800805b502c
 Oops: Kernel access of bad area, sig: 11 [#1]
 NIP [c0000000000388a4] .ioread32+0x4/0x20
 LR [80000000000c6034] .sata_fsl_port_stop+0x44/0xe0 [sata_fsl]
 Call Trace:
  .free_irq+0x1c/0x4e0 (unreliable)
  .ata_host_stop+0x74/0xd0 [libata]
  .release_nodes+0x330/0x3f0
  .device_release_driver_internal+0x178/0x2c0
  .driver_detach+0x64/0xd0
  .bus_remove_driver+0x70/0xf0
  .driver_unregister+0x38/0x80
  .platform_driver_unregister+0x14/0x30
  .fsl_sata_driver_exit+0x18/0xa20 [sata_fsl]
  .__se_sys_delete_module+0x1ec/0x2d0
  .system_call_exception+0xfc/0x1f0
  system_call_common+0xf8/0x200
 ==================================================================

The triggering of the BUG is shown in the following stack:

driver_detach
  device_release_driver_internal
    __device_release_driver
      drv->remove(dev) --> platform_drv_remove/platform_remove
        drv->remove(dev) --> sata_fsl_remove
          iounmap(host_priv->hcr_base);			<---- unmap
          kfree(host_priv);                             <---- free
      devres_release_all
        release_nodes
          dr->node.release(dev, dr->data) --> ata_host_stop
            ap->ops->port_stop(ap) --> sata_fsl_port_stop
                ioread32(hcr_base + HCONTROL)           <---- UAF
            host->ops->host_stop(host)

The iounmap(host_priv->hcr_base) and kfree(host_priv) functions should
not be executed in drv->remove. These functions should be executed in
host_stop after port_stop. Therefore, we move these functions to the
new function sata_fsl_host_stop and bind the new function to host_stop.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2021-47549?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47549?

Apply the vendor's patch.

## Is CVE-2021-47549 being exploited?

There is no known exploitation of CVE-2021-47549 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-2021-47549 and fix it if it is affected.

What it is: CVE-2021-47549 is a high-severity use after free vulnerability in Linux kernel, published on 24 May 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-47549 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-2021-47549/ (Markdown: https://insights.sbomify.com/CVE-2021-47549/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47549
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47549
- OSV: https://osv.dev/vulnerability/CVE-2021-47549

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47549/
Summaries are generated and may contain mistakes; the official description above is the record.