# CVE-2026-89589: acpi/apei/ghes: Use raw_spinlock_t for CXL CPER work locks

> A race condition in the Linux kernel CXL CPER handling can cause a deadlock when a GHES interrupt occurs while holding a spinlock, leading to system 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:** BELL-CVE-2026-89589, DEBIAN-CVE-2026-89589, GHSA-9wp4-w6jg-245j, UBUNTU-CVE-2026-89589

## What is CVE-2026-89589?

CVE-2026-89589 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:

acpi/apei/ghes: Use raw_spinlock_t for CXL CPER work locks

The CXL CPER work registration and unregistration helpers acquire
cxl_cper_work_lock and cxl_cper_prot_err_work_lock with a spinlock
guard(), which leaves local interrupts enabled. The corresponding post
paths (cxl_cper_post_event(), cxl_cper_post_prot_err()) execute in hard
IRQ context (they are called from the GHES error notification path) and
acquire the same locks with an irqsave guard().

If a CPU is holding one of these locks via a spinlock guard() when a GHES
interrupt arrives on the same CPU, the IRQ handler spins on the held lock
waiting for it to release, while the lock holder is preempted by the IRQ.
The result is a deadlock.

Convert both locks from spinlock_t to raw_spinlock_t and use guard() at
all call sites. On PREEMPT_RT kernels spinlock_t is backed by rt_mutex and
sleeping from hard IRQ context is not permitted; raw_spinlock_t is safe in
both contexts.

Add WARN_ONCE to both register functions to surface double-registration
bugs at runtime.

Restructure both unregister functions to clear the global work pointer
under the lock before calling cancel_work_sync(), closing the window
where a CPER interrupt could schedule work on a pointer about to be
freed. Add kfifo_reset() after cancel_work_sync() so stale entries
are not replayed on next module load.

Both kfifos are single-consumer: only one work_struct is registered at
a time, enforced by the WARN_ONCE guard in the register functions.
kfifo_reset() is safe outside the lock because cancel_work_sync() has
already quiesced the consumer, and no new consumer can register until
the current module exit completes and a fresh module init runs.

Remove the redundant cancel_work_sync() call from cxl_ras_exit() and
cxl_pci_driver_exit(). The CPER unregister functions now quiesce
the work internally.

## Which versions are affected by CVE-2026-89589?


## How do I fix CVE-2026-89589?

Apply the vendor's patch.

## Is CVE-2026-89589 being exploited?

There is no known exploitation of CVE-2026-89589 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89589 and fix it if it is affected.

What it is: CVE-2026-89589 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-2026-89589 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-2026-89589/ (Markdown: https://insights.sbomify.com/CVE-2026-89589/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89589
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89589
- OSV: https://osv.dev/vulnerability/CVE-2026-89589

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89589/
Summaries are generated and may contain mistakes; the official description above is the record.