serial: caif: fix use-after-free in caif_serial ldisc_close()

{
  "id": "25cf95e44917779dab33eeeb0e4ad6de693459e8df9b1c011b63fd9ebd1f5e3f",
  "url": "https://osv.dev/vulnerability/CVE-2026-45866",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "serial: caif: fix use-after-free in caif_serial ldisc_close()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: serial: caif: fix use-after-free in caif_serial ldisc_close() There is a use-after-free bug in caif_serial where handle_tx() may access ser->tty after the tty has been freed. The race condition occurs between ldisc_close() and packet transmission: CPU 0 (close) CPU 1 (xmit) ------------- ------------ ldisc_close() tty_kref_put(ser->tty) [tty may be freed here] <-- race window --> caif_xmit() handle_tx() tty = ser->tty // dangling ptr tty->ops->write() // UAF! schedule_work() ser_release() unregister_netdevice() The root cause is that tty_kref_put() is called in ldisc_close() while the network device is still active and can receive packets. Since ser and tty have a 1:1 binding relationship with consistent lifecycles (ser is allocated in ldisc_open and freed in ser_release via unregister_netdevice, and each ser binds exactly one tty), we can safely defer the tty reference release to ser_release() where the network device is unregistered. Fix this by moving tty_kref_put() from ldisc_close() to ser_release(), after unregister_netdevice(). This ensures the tty reference is held as long as the network device exists, preventing the UAF. Note: We save ser->tty before unregister_netdevice() because ser is embedded in netdev's private data and will be freed along with netdev (needs_free_netdev = true). How to reproduce: Add mdelay(500) at the beginning of ldisc_close() to widen the race window, then run the reproducer ",
    "evidence": "osv:CVE-2026-45866",
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    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-45866",
      "aliases": [
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      "modified": "2026-10-28T02:30:36.050140438Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/308e7e4d0a846359685f40aade023aee7b27284c",
        "https://git.kernel.org/stable/c/331e2b7051635780edea248dd08ae2026c126f4a",
        "https://git.kernel.org/stable/c/40962f2bf8cdba63af23aec95ad3f49b689e58e2",
        "https://git.kernel.org/stable/c/4e63d6f68544ae5269ac9735ae5b69b59b5b8725",
        "https://git.kernel.org/stable/c/52731ef4438155cea782fac74e547a327ab9e7c5",
        "https://git.kernel.org/stable/c/5e266ba8d330d3b8e5bc198f238cd8901826cfa1",
        "https://git.kernel.org/stable/c/c8c197aaa56b25a2d54f3aa07e27e228d6c08546",
        "https://git.kernel.org/stable/c/d3c75db4e0460641dbcd274b40867e252d801da1",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/45xxx/CVE-2026-45866.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-45866",
        "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/2026/45xxx/CVE-2026-45866.json"
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    "related_cves": [
      {
        "value": "CVE-2026-45866",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 503162,
  "published_at": "2026-05-27T12:15:46.135+00:00"
}