# CVE-2024-35844: f2fs: compress: fix reserve_cblocks counting error when out of space

> A logic error in the Linux kernel's f2fs compression module causes files to become unrepairable when disk space is exhausted, leading to data loss or 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:** 17 May 2024
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2024-35844, DEBIAN-CVE-2024-35844, GHSA-7f94-q32g-r8m7, ROOT-OS-DEBIAN-11-CVE-2024-35844, UBUNTU-CVE-2024-35844

## What is CVE-2024-35844?

CVE-2024-35844 is a medium-severity denial of service vulnerability in Linux kernel, published on 17 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:

f2fs: compress: fix reserve_cblocks counting error when out of space

When a file only needs one direct_node, performing the following
operations will cause the file to be unrepairable:

unisoc # ./f2fs_io compress test.apk
unisoc #df -h | grep dm-48
/dev/block/dm-48 112G 112G 1.2M 100% /data

unisoc # ./f2fs_io release_cblocks test.apk
924
unisoc # df -h | grep dm-48
/dev/block/dm-48 112G 112G 4.8M 100% /data

unisoc # dd if=/dev/random of=file4 bs=1M count=3
3145728 bytes (3.0 M) copied, 0.025 s, 120 M/s
unisoc # df -h | grep dm-48
/dev/block/dm-48 112G 112G 1.8M 100% /data

unisoc # ./f2fs_io reserve_cblocks test.apk
F2FS_IOC_RESERVE_COMPRESS_BLOCKS failed: No space left on device

adb reboot
unisoc # df -h  | grep dm-48
/dev/block/dm-48             112G 112G   11M 100% /data
unisoc # ./f2fs_io reserve_cblocks test.apk
0

This is because the file has only one direct_node. After returning
to -ENOSPC, reserved_blocks += ret will not be executed. As a result,
the reserved_blocks at this time is still 0, which is not the real
number of reserved blocks. Therefore, fsck cannot be set to repair
the file.

After this patch, the fsck flag will be set to fix this problem.

unisoc # df -h | grep dm-48
/dev/block/dm-48             112G 112G  1.8M 100% /data
unisoc # ./f2fs_io reserve_cblocks test.apk
F2FS_IOC_RESERVE_COMPRESS_BLOCKS failed: No space left on device

adb reboot then fsck will be executed
unisoc # df -h  | grep dm-48
/dev/block/dm-48             112G 112G   11M 100% /data
unisoc # ./f2fs_io reserve_cblocks test.apk
924

## Which versions are affected by CVE-2024-35844?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-35844?

Apply the vendor's patch.

## Is CVE-2024-35844 being exploited?

There is no known exploitation of CVE-2024-35844 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-2024-35844 and fix it if it is affected.

What it is: CVE-2024-35844 is a medium-severity denial of service vulnerability in Linux kernel, published on 17 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-2024-35844 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-2024-35844/ (Markdown: https://insights.sbomify.com/CVE-2024-35844/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-35844
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-35844
- OSV: https://osv.dev/vulnerability/CVE-2024-35844

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-35844/
Summaries are generated and may contain mistakes; the official description above is the record.