virtio_balloon: quiesce balloon work before device shutdown

Summary

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.

Timeline

1. Sep 17, 2026, 4:06 PM UTCCVE published
2. Oct 30, 2026, 12:34 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 6.1.191 · fixed in 6.2; From 6.6.160 · fixed in 6.7; From 6.12.114 · fixed in 6.13; From 6.14.9 · fixed in 6.15

• Linux Linux

  6.15

• KernelLinux

  From 6.15.0 · fixed in 6.18.52; From 6.19.0 · fixed in 7.2.6

References 3