# CVE-2024-39486: drm/drm_file: Fix pid refcounting race

> A race condition in the Linux kernel DRM subsystem allows a use-after-free of a struct pid, potentially enabling local privilege escalation or code execution.

- **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:** 6 Jul 2024
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2024-39486, DEBIAN-CVE-2024-39486, GHSA-wccc-2qv8-6647, UBUNTU-CVE-2024-39486

## What is CVE-2024-39486?

CVE-2024-39486 is a high-severity use after free vulnerability in Linux kernel, published on 6 Jul 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:

drm/drm_file: Fix pid refcounting race

<maarten.lankhorst@linux.intel.com>, Maxime Ripard
<mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>

filp->pid is supposed to be a refcounted pointer; however, before this
patch, drm_file_update_pid() only increments the refcount of a struct
pid after storing a pointer to it in filp->pid and dropping the
dev->filelist_mutex, making the following race possible:

process A               process B
=========               =========
                        begin drm_file_update_pid
                        mutex_lock(&dev->filelist_mutex)
                        rcu_replace_pointer(filp->pid, <pid B>, 1)
                        mutex_unlock(&dev->filelist_mutex)
begin drm_file_update_pid
mutex_lock(&dev->filelist_mutex)
rcu_replace_pointer(filp->pid, <pid A>, 1)
mutex_unlock(&dev->filelist_mutex)
get_pid(<pid A>)
synchronize_rcu()
put_pid(<pid B>)   *** pid B reaches refcount 0 and is freed here ***
                        get_pid(<pid B>)   *** UAF ***
                        synchronize_rcu()
                        put_pid(<pid A>)

As far as I know, this race can only occur with CONFIG_PREEMPT_RCU=y
because it requires RCU to detect a quiescent state in code that is not
explicitly calling into the scheduler.

This race leads to use-after-free of a "struct pid".
It is probably somewhat hard to hit because process A has to pass
through a synchronize_rcu() operation while process B is between
mutex_unlock() and get_pid().

Fix it by ensuring that by the time a pointer to the current task's pid
is stored in the file, an extra reference to the pid has been taken.

This fix also removes the condition for synchronize_rcu(); I think
that optimization is unnecessary complexity, since in that case we
would usually have bailed out on the lockless check above.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2024-39486?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-39486?

Apply the vendor's patch.

## Is CVE-2024-39486 being exploited?

There is no known exploitation of CVE-2024-39486 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-2024-39486 and fix it if it is affected.

What it is: CVE-2024-39486 is a high-severity use after free vulnerability in Linux kernel, published on 6 Jul 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-2024-39486 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-2024-39486/ (Markdown: https://insights.sbomify.com/CVE-2024-39486/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-39486
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-39486
- OSV: https://osv.dev/vulnerability/CVE-2024-39486

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-39486/
Summaries are generated and may contain mistakes; the official description above is the record.