# CVE-2026-97521: gfs2: fix quota init duplicate scan

> A local attacker can cause a kernel crash in the GFS2 filesystem on PREEMPT_RT systems by triggering a sleeping function call in an atomic context.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** AZL-103757, BELL-CVE-2026-97521, DEBIAN-CVE-2026-97521, GHSA-jgmg-x8vv-p7hr, UBUNTU-CVE-2026-97521

## What is CVE-2026-97521?

CVE-2026-97521 is a denial of service vulnerability in Linux, published on 24 Sep 2026. 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:

gfs2: fix quota init duplicate scan

gfs2_quota_init() checks for duplicate quota_change IDs while holding
qd_lock and the quota hash bucket bitlock. That path used
gfs2_qd_search_bucket(), which takes a lockref reference via
lockref_get_not_dead().

On PREEMPT_RT this may sleep, which is not allowed under the bucket
bitlock, triggering "sleeping function called from invalid context".

Use a no-ref bucket lookup in this path, then continue duplicate
handling without taking a lockref there.

Refactor gfs2_qd_search_bucket() to build on top of the no-ref helper
so lookup traversal stays in one place.

This patch fixes a bug reported by syzbot.

## Which versions are affected by CVE-2026-97521?


## How do I fix CVE-2026-97521?

Apply the vendor's patch.

## Is CVE-2026-97521 being exploited?

There is no known exploitation of CVE-2026-97521 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97521 and fix it if it is affected.

What it is: CVE-2026-97521 is a denial of service vulnerability in Linux, published on 24 Sep 2026. 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-2026-97521 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-2026-97521/ (Markdown: https://insights.sbomify.com/CVE-2026-97521/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97521
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97521
- OSV: https://osv.dev/vulnerability/CVE-2026-97521

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97521/
Summaries are generated and may contain mistakes; the official description above is the record.