Bug 2540419 (CVE-2026-97478)
| Summary: | CVE-2026-97478 kernel: virt: acrn: Fix irqfd use-after-free during eventfd shutdown | ||
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| Product: | [Other] Security Response | Reporter: | OSIDB Bzimport <bzimport> |
| Component: | vulnerability | Assignee: | Product Security DevOps Team <prodsec-dev> |
| Status: | NEW --- | QA Contact: | |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | unspecified | CC: | akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers |
| Target Milestone: | --- | Keywords: | Security |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | --- | |
| Doc Text: |
A flaw was found in the Linux kernel's ACRN hypervisor driver. A race condition during interrupt file descriptor (irqfd) shutdown can lead to a use-after-free memory error when an irqfd is deassigned while event notification cleanup is concurrently processed. A local attacker could exploit this vulnerability to cause a system crash, resulting in a Denial of Service (DoS), or potentially escalate privileges.
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Story Points: | --- |
| Clone Of: | Environment: | ||
| Last Closed: | Type: | --- | |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
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.