UBUNTU-CVE-2026-98841: Null Pointer Dereference

In the Linux kernel, the following vulnerability has been resolved: virt: vmgenid: set driverdata before registering notification handlers Both probe paths register their notification handler before assigning driverdata, which the handler dereferences. In the devicetree path, the notification IRQ can fire as soon as devmrequestirq() registers the handler: the interrupt may already be pending at probe time, for example when a VMM injects the generation-changed notification while restoring a guest from a snapshot that was taken before the driver had probed (Firecracker does exactly this on snapshot restore). The IRQ is also requested with IRQFSHARED, so another device sharing the line can trigger the handler just as early. The handler then calls vmgenidnotify(), which dereferences the still-NULL driverdata and panics: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010 CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.18.38+ #1 PREEMPT(none) Hardware name: linux,dummy-virt (DT) pc : vmgenidnotify.isra.0+0x24/0x8c lr : vmgenidofirqhandler+0x14/0x34 Call trace: vmgenidnotify.isra.0+0x24/0x8c (P) vmgenidofirqhandler+0x14/0x34 handleirqeventpercpu+0x44/0x1bc handleirqevent+0x4c/0xb4 handlefasteoiirq+0xf8/0x1f8 The ACPI path has the same ordering problem: the handler is installed with acpiinstallnotifyhandler() before driverdata is assigned. ACPI notifications are dispatched asynchronously from a workqueue, so the window is narrow, but a notification arriving between the two calls hits the same NULL dereference. Assign driverdata before registering the handlers. The state is fully initialized at that point, so the handlers are safe to run. Should registration fail, the probe error path leaves no dangling pointer behind: the driver core clears driverdata in deviceunbindcleanup().