# CVE-2026-98344: dmaengine: Fix device kref underflow in dma_chan_put()

> A reference counting bug in the Linux kernel DMA engine can cause a use-after-free condition, leading to denial of service when specific client interactions occur.

- **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:** AZL-106251, BELL-CVE-2026-98344, DEBIAN-CVE-2026-98344, GHSA-g4c2-fm3r-x4gh, UBUNTU-CVE-2026-98344

## What is CVE-2026-98344?

CVE-2026-98344 is an use after free 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:

dmaengine: Fix device kref underflow in dma_chan_put()

dma_chan_get() takes chan->device->ref only on the slow path:

	/* no kref on fast path */
	if (chan->client_count) {
		__module_get(owner);
		chan->client_count++;
		return 0;
	}
	if (!try_module_get(owner))
		return -ENODEV;
	if (!dma_device_get(chan->device)) { // calls kref_get_unless_zero()

dma_chan_put() drops the ref unconditionally, so every fast-path
get/put pair drops one extra device reference.

The bug fires when two conditions hold together: a non-private
provider has a persistent client holding chan->client_count > 0
and another client cycles dmaengine_get()/dmaengine_put().
When the kref hits zero, the subsequent dma_find_channel() returns
NULL even though the provider module is still loaded.

Fix this by dropping device->ref only on the last put, matching the
single slow-path get.

## Which versions are affected by CVE-2026-98344?


## How do I fix CVE-2026-98344?

Apply the vendor's patch.

## Is CVE-2026-98344 being exploited?

There is no known exploitation of CVE-2026-98344 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98344 and fix it if it is affected.

What it is: CVE-2026-98344 is an use after free 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-2026-98344 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-2026-98344/ (Markdown: https://insights.sbomify.com/CVE-2026-98344/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98344
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98344
- OSV: https://osv.dev/vulnerability/CVE-2026-98344

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98344/
Summaries are generated and may contain mistakes; the official description above is the record.