CVE-2026-97478
Received
Received - Intake
Use-After-Free in ACRN Hypervisor irqfd Handling
Vulnerability report for CVE-2026-97478, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-09-24
Last updated on: 2026-09-28
Assigner: kernel.org
Description
Description
In the Linux kernel, the following vulnerability has been resolved:
virt: acrn: Fix irqfd use-after-free during eventfd shutdown
acrn_irqfd_deassign() and the eventfd EPOLLHUP wakeup can race and free
the same struct hsm_irqfd:
CPU0 CPU1
---- ----
eventfd_release()
wake_up_poll(EPOLLHUP)
hsm_irqfd_wakeup()
queue_work(&irqfd->shutdown)
acrn_irqfd_deassign()
hsm_irqfd_shutdown()
list_del_init()
eventfd_ctx_remove_wait_queue()
eventfd_ctx_put()
kfree(irqfd)
hsm_irqfd_shutdown_work()
container_of(work, ..., shutdown)
irqfd->vm <-- use-after-free
The deassign path freed the irqfd while a shutdown work item was
already queued by EPOLLHUP (or vice versa), so the work item could
resurrect a dangling pointer through container_of().
Switch to the lifetime model used by KVM irqfds:
- Deassign/deinit only deactivate the irqfd: remove it from vm->irqfds
under irqfds_lock and queue the cleanup work.
- hsm_irqfd_shutdown_work() becomes the sole owner that unhooks the
eventfd waitqueue entry, drops the eventfd reference and frees the
irqfd.
- A new HSM_IRQFD_FLAG_SHUTDOWN bit guarded by test_and_set_bit()
ensures the cleanup work is queued at most once, no matter how many
of {EPOLLHUP, deassign, deinit} fire concurrently. This is safe to
call from the waitqueue callback, which runs with wqh->lock held and
IRQs disabled and therefore cannot take irqfds_lock.
- acrn_irqfd_deassign() flushes vm->irqfd_wq before returning so the
eventfd is fully detached on return. acrn_irqfd_deinit() deactivates
every irqfd, flushes the workqueue and only then destroys it, so no
path can queue_work() onto a torn-down workqueue.
- acrn_irqfd_assign() now installs the eventfd waitqueue entry and
publishes the irqfd to vm->irqfds under irqfds_lock, so the irqfd is
never visible to deassign/deinit before its waitqueue entry is in
place, and any EPOLLHUP that fires in the assign window queues
cleanup work that blocks on irqfds_lock until publication is done.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| acrn | acrn | * |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-UNKNOWN |
