UBUNTU-CVE-2026-90129: Medium severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: virtioballoon: quiesce balloon work before device shutdown Commit 8bd2fa086a04 ("virtio: break and reset virtio devices on deviceshutdown()") added a generic virtio bus .shutdown handler that breaks and resets every virtio device during deviceshutdown(), i.e. on reboot and kexec. virtioballoon 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, virtqueueaddinbuf() in virtballoonfreepagereport() returns -EIO and trips its WARNONONCE(). On a kernel booted with paniconwarn that turns an ordinary reboot, for example a kexec based upgrade, into a fatal panic in the middle of deviceshutdown(), so the machine never reaches the new kernel. Relaxing that single WARNONONCE() would only hide the symptom: the inflate/deflate and OOM paths do not warn, they call waitevent(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 virtballoonquiesce() helper while the device is still alive, and only then breaks and resets it via virtiodeviceshutdown(). Unlike virtballoonremove() the balloon workqueue is not destroyed, as shutdown does not free the device and cancelworksync() together with stopupdate already prevent any further work from being queued.