# CVE-2026-98223: mm: filemap: retain mapped dropbehind folios

> A Linux kernel bug in filemap handling can cause a sleeping-in-atomic warning, potentially leading to system instability or denial of service.

- **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:** 6 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-98223, DEBIAN-CVE-2026-98223, GHSA-h9mh-jjx8-7v74, UBUNTU-CVE-2026-98223

## What is CVE-2026-98223?

CVE-2026-98223 is a denial of service vulnerability in Linux, published on 6 Oct 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:

mm: filemap: retain mapped dropbehind folios

Fault-around can map ready dropbehind folios without going through the
normal page-cache lookup that clears dropbehind.  A mapping represents a
competing cached user, so retain the folio instead of forcibly unmapping
it when writeback completes.

For a mapped folio, folio_unmap_invalidate() can call
unmap_mapping_folio(), which takes i_mmap_rwsem and may sleep.  Retaining
mapped folios avoids this path when folio_end_dropbehind() runs in
non-preemptible task context.

Tal was able to trigger a sleeping-in-atomic warning due to this [1].

Unmapped dropbehind folios continue through the existing invalidation path.

## Which versions are affected by CVE-2026-98223?


## How do I fix CVE-2026-98223?

Apply the vendor's patch.

## Is CVE-2026-98223 being exploited?

There is no known exploitation of CVE-2026-98223 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98223 and fix it if it is affected.

What it is: CVE-2026-98223 is a denial of service vulnerability in Linux, published on 6 Oct 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-2026-98223 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-2026-98223/ (Markdown: https://insights.sbomify.com/CVE-2026-98223/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98223
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98223
- OSV: https://osv.dev/vulnerability/CVE-2026-98223

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98223/
Summaries are generated and may contain mistakes; the official description above is the record.