# CVE-2024-46704: workqueue: Fix spruious data race in __flush_work()

> A spurious data race in the Linux kernel workqueue subsystem triggered KCSAN warnings but had no functional security impact.

- **Severity:** Medium 4.7 (`CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/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:** 13 Sep 2024
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2024-46704, DEBIAN-CVE-2024-46704, GHSA-mgxj-66hj-35x8, UBUNTU-CVE-2024-46704

## What is CVE-2024-46704?

CVE-2024-46704 is a medium-severity vulnerability in Linux kernel, published on 13 Sep 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:

workqueue: Fix spruious data race in __flush_work()

When flushing a work item for cancellation, __flush_work() knows that it
exclusively owns the work item through its PENDING bit. 134874e2eee9
("workqueue: Allow cancel_work_sync() and disable_work() from atomic
contexts on BH work items") added a read of @work->data to determine whether
to use busy wait for BH work items that are being canceled. While the read
is safe when @from_cancel, @work->data was read before testing @from_cancel
to simplify code structure:

	data = *work_data_bits(work);
	if (from_cancel &&
	    !WARN_ON_ONCE(data & WORK_STRUCT_PWQ) && (data & WORK_OFFQ_BH)) {

While the read data was never used if !@from_cancel, this could trigger
KCSAN data race detection spuriously:

  ==================================================================
  BUG: KCSAN: data-race in __flush_work / __flush_work

  write to 0xffff8881223aa3e8 of 8 bytes by task 3998 on cpu 0:
   instrument_write include/linux/instrumented.h:41 [inline]
   ___set_bit include/asm-generic/bitops/instrumented-non-atomic.h:28 [inline]
   insert_wq_barrier kernel/workqueue.c:3790 [inline]
   start_flush_work kernel/workqueue.c:4142 [inline]
   __flush_work+0x30b/0x570 kernel/workqueue.c:4178
   flush_work kernel/workqueue.c:4229 [inline]
   ...

  read to 0xffff8881223aa3e8 of 8 bytes by task 50 on cpu 1:
   __flush_work+0x42a/0x570 kernel/workqueue.c:4188
   flush_work kernel/workqueue.c:4229 [inline]
   flush_delayed_work+0x66/0x70 kernel/workqueue.c:4251
   ...

  value changed: 0x0000000000400000 -> 0xffff88810006c00d

Reorganize the code so that @from_cancel is tested before @work->data is
accessed. The only problem is triggering KCSAN detection spuriously. This
shouldn't need READ_ONCE() or other access qualifiers.

No functional changes.

## Which versions are affected by CVE-2024-46704?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-46704?

Apply the vendor's patch.

## Is CVE-2024-46704 being exploited?

There is no known exploitation of CVE-2024-46704 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-2024-46704 and fix it if it is affected.

What it is: CVE-2024-46704 is a medium-severity vulnerability in Linux kernel, published on 13 Sep 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-2024-46704 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-2024-46704/ (Markdown: https://insights.sbomify.com/CVE-2024-46704/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-46704
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-46704
- OSV: https://osv.dev/vulnerability/CVE-2024-46704

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-46704/
Summaries are generated and may contain mistakes; the official description above is the record.