# CVE-2025-40150: f2fs: fix to avoid migrating empty section

> A race condition in the Linux kernel f2fs filesystem allows local attackers to trigger a filesystem shutdown, causing denial of service.

- **Severity:** Not scored
- **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:** 12 Nov 2025
- **Updated:** 23 May 2026
- **Also known as:** BELL-CVE-2025-40150, DEBIAN-CVE-2025-40150, GHSA-xxcp-92h2-x7r7, ROOT-OS-DEBIAN-13-CVE-2025-40150, ROOT-OS-UBUNTU-2404-CVE-2025-40150, UBUNTU-CVE-2025-40150

## What is CVE-2025-40150?

CVE-2025-40150 is a vulnerability in Linux, published on 12 Nov 2025. 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: fix to avoid migrating empty section

It reports a bug from device w/ zufs:

F2FS-fs (dm-64): Inconsistent segment (173822) type [1, 0] in SSA and SIT
F2FS-fs (dm-64): Stopped filesystem due to reason: 4

Thread A				Thread B
- f2fs_expand_inode_data
 - f2fs_allocate_pinning_section
  - f2fs_gc_range
   - do_garbage_collect w/ segno #x
					- writepage
					 - f2fs_allocate_data_block
					  - new_curseg
					   - allocate segno #x

The root cause is: fallocate on pinning file may race w/ block allocation
as above, result in do_garbage_collect() from fallocate() may migrate
segment which is just allocated by a log, the log will update segment type
in its in-memory structure, however GC will get segment type from on-disk
SSA block, once segment type changes by log, we can detect such
inconsistency, then shutdown filesystem.

In this case, on-disk SSA shows type of segno #173822 is 1 (SUM_TYPE_NODE),
however segno #173822 was just allocated as data type segment, so in-memory
SIT shows type of segno #173822 is 0 (SUM_TYPE_DATA).

Change as below to fix this issue:
- check whether current section is empty before gc
- add sanity checks on do_garbage_collect() to avoid any race case, result
in migrating segment used by log.
- btw, it fixes misc issue in printed logs: "SSA and SIT" -> "SIT and SSA".

## Which versions are affected by CVE-2025-40150?


## How do I fix CVE-2025-40150?

Apply the vendor's patch.

## Is CVE-2025-40150 being exploited?

There is no known exploitation of CVE-2025-40150 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-40150 and fix it if it is affected.

What it is: CVE-2025-40150 is a vulnerability in Linux, published on 12 Nov 2025. 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-2025-40150 in the wild and no public exploit code.

Affected product: Linux. 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-2025-40150/ (Markdown: https://insights.sbomify.com/CVE-2025-40150/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-40150
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-40150
- OSV: https://osv.dev/vulnerability/CVE-2025-40150

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-40150/
Summaries are generated and may contain mistakes; the official description above is the record.