# CVE-2024-56755: netfs/fscache: Add a memory barrier for FSCACHE_VOLUME_CREATING

> A missing memory barrier in the Linux kernel fscache module can cause an indefinite wait, leading to a denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/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:** 29 Dec 2024
- **Updated:** 11 May 2026
- **Also known as:** AZL-54895, BELL-CVE-2024-56755, DEBIAN-CVE-2024-56755, GHSA-2cxg-hjm3-xmvr, UBUNTU-CVE-2024-56755

## What is CVE-2024-56755?

CVE-2024-56755 is a medium-severity vulnerability in Linux kernel, published on 29 Dec 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:

netfs/fscache: Add a memory barrier for FSCACHE_VOLUME_CREATING

In fscache_create_volume(), there is a missing memory barrier between the
bit-clearing operation and the wake-up operation. This may cause a
situation where, after a wake-up, the bit-clearing operation hasn't been
detected yet, leading to an indefinite wait. The triggering process is as
follows:

  [cookie1]                [cookie2]                  [volume_work]
fscache_perform_lookup
  fscache_create_volume
                        fscache_perform_lookup
                          fscache_create_volume
			                        fscache_create_volume_work
                                                  cachefiles_acquire_volume
                                                  clear_and_wake_up_bit
    test_and_set_bit
                            test_and_set_bit
                              goto maybe_wait
      goto no_wait

In the above process, cookie1 and cookie2 has the same volume. When cookie1
enters the -no_wait- process, it will clear the bit and wake up the waiting
process. If a barrier is missing, it may cause cookie2 to remain in the
-wait- process indefinitely.

In commit 3288666c7256 ("fscache: Use clear_and_wake_up_bit() in
fscache_create_volume_work()"), barriers were added to similar operations
in fscache_create_volume_work(), but fscache_create_volume() was missed.

By combining the clear and wake operations into clear_and_wake_up_bit() to
fix this issue.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2024-56755?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-56755?

Apply the vendor's patch.

## Is CVE-2024-56755 being exploited?

There is no known exploitation of CVE-2024-56755 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-2024-56755 and fix it if it is affected.

What it is: CVE-2024-56755 is a medium-severity vulnerability in Linux kernel, published on 29 Dec 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-2024-56755 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-2024-56755/ (Markdown: https://insights.sbomify.com/CVE-2024-56755/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-56755
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-56755
- OSV: https://osv.dev/vulnerability/CVE-2024-56755

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-56755/
Summaries are generated and may contain mistakes; the official description above is the record.