# CVE-2026-89490: ocfs2: fix readdir position truncation on 32-bit kernels

> A 32-bit integer overflow in the OCFS2 filesystem causes infinite loops during directory enumeration on large files, leading to 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:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-100220, BELL-CVE-2026-89490, DEBIAN-CVE-2026-89490, GHSA-3jg7-r7pg-8654, UBUNTU-CVE-2026-89490

## What is CVE-2026-89490?

CVE-2026-89490 is a vulnerability in Linux, published on 11 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:

ocfs2: fix readdir position truncation on 32-bit kernels

In ocfs2_dir_foreach_blk_el(), the directory cookie position is
rebuilt with

	ctx->pos = (ctx->pos & ~(sb->s_blocksize - 1)) | offset;

`ctx->pos` is loff_t (signed 64-bit), while `sb->s_blocksize` is
unsigned long.  On 32-bit kernels unsigned long is 32-bit, so the mask

	~(sb->s_blocksize - 1)

is computed as a 32-bit unsigned value (e.g. 0xfffff000 for a 4 KiB
block size).  In the AND expression with the 64-bit `ctx->pos`, that
unsigned operand is zero-extended to 64 bits per the usual arithmetic
conversions, yielding 0x00000000fffff000.  The high 32 bits of
`ctx->pos` are silently cleared, even though directory size is
allowed to exceed 4 GiB.

When readdir() crosses the 4 GiB boundary on a 32-bit kernel the
position is reset back into the first 4 GiB block, making the
re-validation path re-enumerate already-returned dirents indefinitely.

This is ocfs2_dir_foreach_blk_el(), the extent-list readdir path taken
for all non-inline directories, so a directory large enough to cross
4 GiB reaches it.

This is the same class of bug that commit 3dce5bb82c97 ("exfat: Fix
bitwise operation having different size") fixed in exfat, and the
fix mirrors the equivalent ext4 fix in this series.  Cast the operand
to loff_t so the mask is 64-bit before the AND:

	ctx->pos = (ctx->pos & ~((loff_t)sb->s_blocksize - 1)) | offset;

64-bit kernels are unaffected.

## Which versions are affected by CVE-2026-89490?


## How do I fix CVE-2026-89490?

Apply the vendor's patch.

## Is CVE-2026-89490 being exploited?

There is no known exploitation of CVE-2026-89490 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89490 and fix it if it is affected.

What it is: CVE-2026-89490 is a vulnerability in Linux, published on 11 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-2026-89490 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-2026-89490/ (Markdown: https://insights.sbomify.com/CVE-2026-89490/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89490
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89490
- OSV: https://osv.dev/vulnerability/CVE-2026-89490

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89490/
Summaries are generated and may contain mistakes; the official description above is the record.