Linux Kernel vmgenid Driver NULL Deref via Early IRQ Notification
CVE-2026-98841 Published on October 18, 2026
virt: vmgenid: set driver_data before registering notification handlers
In the Linux kernel, the following vulnerability has been resolved:
virt: vmgenid: set driver_data before registering notification handlers
Both probe paths register their notification handler before assigning
driver_data, which the handler dereferences.
In the devicetree path, the notification IRQ can fire as soon as
devm_request_irq() 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 IRQF_SHARED,
so another device sharing the line can trigger the handler just as
early. The handler then calls vmgenid_notify(), which dereferences the
still-NULL driver_data 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 : vmgenid_notify.isra.0+0x24/0x8c
lr : vmgenid_of_irq_handler+0x14/0x34
Call trace:
vmgenid_notify.isra.0+0x24/0x8c (P)
vmgenid_of_irq_handler+0x14/0x34
__handle_irq_event_percpu+0x44/0x1bc
handle_irq_event+0x4c/0xb4
handle_fasteoi_irq+0xf8/0x1f8
The ACPI path has the same ordering problem: the handler is installed
with acpi_install_notify_handler() before driver_data 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 driver_data 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 driver_data in device_unbind_cleanup().
Products Associated with CVE-2026-98841
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Affected Versions
Linux:- Version e07606713a908eee8099883c8c830ebe33aaf748 and below 538fe5efaa9704ad820ba34b4f9df135ca873d79 is affected.
- Version e07606713a908eee8099883c8c830ebe33aaf748 and below 7a1e8daeaa466c6aaffa223e1afe9cfeece0dd47 is affected.
- Version e07606713a908eee8099883c8c830ebe33aaf748 and below 8f42954ad8bf9bdbf574f2c437ad30cb2601f401 is affected.
- Version e07606713a908eee8099883c8c830ebe33aaf748 and below 9f8139c6145cf17d690d6c414d43b4c0bef632fb is affected.
- Version 6.10 is affected.
- Before 6.10 is unaffected.
- Version 6.12.113, <= 6.12.* is unaffected.
- Version 6.18.56, <= 6.18.* is unaffected.
- Version 7.2.10, <= 7.2.* is unaffected.
- Version 7.3-rc6, <= * is unaffected.