# CVE-2026-98521: drm/i915: fix incorrect RCU teardown order

> A race condition in the i915 DRM driver causes an infinite loop during GEM object destruction, leading to local 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:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-109427, BELL-CVE-2026-98521, DEBIAN-CVE-2026-98521, GHSA-7hvf-3rfm-fg86, UBUNTU-CVE-2026-98521

## What is CVE-2026-98521?

CVE-2026-98521 is a vulnerability in Linux, published on 18 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:

drm/i915: fix incorrect RCU teardown order

i915_gem_busy_ioctl uses dma_resv_for_each_fence_unlocked() to iterate
over the fences in an GEM object without holding a reference but only
the RCU read side lock.

What can happen here is that the GEM object is destroyed concurrently
while i915_gem_busy_ioctl is still running. This won't free the GEM
objects memory, but still drops all the dma_fence references.

Now when dma_resv_for_each_fence_unlocked() sees a destroyed dma_fence it
assumes that a new fence list was installed and re-starts the loop.

But in the case of a destroyed GEM object a new fence list is never
installed, only the old one freed and therefore the iteration never
finishes resulting in an endless loop.

The solution is to drop the fence references only after the RCU grace
period.

The fixes tag is not necessary the patch introducing the problem, but the
one making it so worse that we need to address it.

This problem was pointed out by Sashiko-bot.

(cherry picked from commit 5113479556025093bf8133bb2dcaa33be2d50921)

## Which versions are affected by CVE-2026-98521?


## How do I fix CVE-2026-98521?

Apply the vendor's patch.

## Is CVE-2026-98521 being exploited?

There is no known exploitation of CVE-2026-98521 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98521 and fix it if it is affected.

What it is: CVE-2026-98521 is a vulnerability in Linux, published on 18 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-2026-98521 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-2026-98521/ (Markdown: https://insights.sbomify.com/CVE-2026-98521/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98521
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98521
- OSV: https://osv.dev/vulnerability/CVE-2026-98521

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98521/
Summaries are generated and may contain mistakes; the official description above is the record.