virt: acrn: Fix irqfd use-after-free during eventfd shutdown

{
  "id": "dfa0b1301f1879ce0593e4342dbffe0731849f4fd576b2f374ce4095cd97d726",
  "url": "https://osv.dev/vulnerability/CVE-2026-97478",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "virt: acrn: Fix irqfd use-after-free during eventfd shutdown",
    "summary": "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() deactivate",
    "evidence": "osv:CVE-2026-97478",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.191",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.160",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.114",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.53",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-97478",
      "aliases": [
        "CVE-2026-97478"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
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              "type": "GIT",
              "events": [
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                {
                  "fixed": "dccf23a72a6c5ec8d9eab2a7f98e186af6eaff48"
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            {
              "type": "ECOSYSTEM",
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                  "introduced": "5.12.0"
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              "type": "ECOSYSTEM",
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          ],
          "package": {
            "name": "Kernel",
            "ecosystem": "Linux"
          },
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-97478.json"
          }
        }
      ],
      "modified": "2026-11-01T02:30:50.625706845Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/0e1152f689847b9db2f05454775d34610c1424c2",
        "https://git.kernel.org/stable/c/666c7f9e07925aa0863348f960e09bb89f8f05a3",
        "https://git.kernel.org/stable/c/6e9e007ee1dfb54bc2d070550308077ec28dbaec",
        "https://git.kernel.org/stable/c/d8156aacfcabb81f52c20ef89094945434d08079",
        "https://git.kernel.org/stable/c/dccf23a72a6c5ec8d9eab2a7f98e186af6eaff48",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/97xxx/CVE-2026-97478.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-97478",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/97xxx/CVE-2026-97478.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-97478",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 509245,
  "published_at": "2026-09-24T16:04:20.263+00:00"
}