CVE-2026-90129: virtio_balloon: quiesce balloon work before device shutdown

Severity: unknown
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-17 · updated 2026-10-30

Description

In the Linux kernel, the following vulnerability has been resolved: virtio_balloon: quiesce balloon work before device shutdown Commit 8bd2fa086a04 ("virtio: break and reset virtio devices on device_shutdown()") added a generic virtio bus .shutdown handler that breaks and resets every virtio device during device_shutdown(), i.e. on reboot and kexec. virtio_balloon provides no .shutdown of its own, so that generic path runs while the balloon's asynchronous work is still armed. Once the device has been broken, virtqueue_add_inbuf() in virtballoon_free_page_report() returns -EIO and trips its WARN_ON_ONCE(). On a kernel booted with panic_on_warn that turns an ordinary reboot, for example a kexec based upgrade, into a fatal panic in the middle of device_shutdown(), so the machine never reaches the new kernel. Relaxing that single WARN_ON_ONCE() would only hide the symptom: the inflate/deflate and OOM paths do not warn, they call wait_event(vb->acked, ...) and would instead block forever on a broken queue that can no longer complete. The device has to be quiesced, not just kept quiet. Add a .shutdown handler that quiesces the balloon via the shared virtballoon_quiesce() helper while the device is still alive, and only then breaks and resets it via virtio_device_shutdown(). Unlike virtballoon_remove() the balloon workqueue is not destroyed, as shutdown does not free the device and cancel_work_sync() together with stop_update already prevent any further work from being queued.

Affected products

Linux: from 6.1.191 before 6.2; from 6.6.160 before 6.7; from 6.12.114 before 6.13; from 6.14.9 before 6.15 — fixed in 6.2, 6.7, 6.13, 6.15

How to fix

Upgrade to a fixed version: Linux 6.2, 6.7, 6.13, 6.15. Check the vendor advisory for mitigations.

References

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