ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation

{
  "id": "774a128543471ee3ae6a46ee2df0c010197e91a9cf5abde27b9be2f17cef1273",
  "url": "https://osv.dev/vulnerability/CVE-2026-64396",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation When a blocking byte-range lock request is deferred in the FILE_LOCK_DEFERRED path, ksmbd registers the asynchronous work into the connection's async_requests list via setup_async_work(). The cancel callback smb2_remove_blocked_lock() holds a reference to the flock. If the lock waiter is subsequently woken up but the work state is no longer KSMBD_WORK_ACTIVE (e.g., due to a concurrent cancellation), the cleanup path calls locks_free_lock(flock) without dequeuing the work from the async_requests list. Concurrently, smb2_cancel() walks the list under conn->request_lock and invokes the cancel callback, which then dereferences the already freed 'flock'. This leads to a slab-use-after-free inside __wake_up_common. Fix this by restructuring the cleanup logic after the worker returns from ksmbd_vfs_posix_lock_wait(). Move list_del(&smb_lock->llist) and release_async_work(work) to the top of the cleanup block. This guarantees that the async work is completely dequeued and serialized under conn->request_lock before locks_free_lock(flock) is called, rendering the flock unreachable for any concurrent smb2_cancel().",
    "evidence": "osv:CVE-2026-64396",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
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        "prerequisites": [],
        "fixed_versions": [
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    "severity": "high",
    "structured": {
      "id": "CVE-2026-64396",
      "aliases": [
        "CVE-2026-64396"
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      "metrics": [
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          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
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      "modified": "2026-10-28T02:30:53.358864454Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/367c42a611fe488b7b03f1f6737f4dee0e8b20a2",
        "https://git.kernel.org/stable/c/463bbd79698513af4dad50fe1c573825f297ca2e",
        "https://git.kernel.org/stable/c/5aa1cb01155f96824003baf7997cdf1f150caba3",
        "https://git.kernel.org/stable/c/5c75275c0fc9a2deb0d8f5604edcb16f288171c8",
        "https://git.kernel.org/stable/c/7703fd9aba1f2483c8e55f9ff73b7663e0761ed9",
        "https://git.kernel.org/stable/c/d20d1c8ba5765d1d12eefc0aee6385ab3f240e1e",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64396.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-64396",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
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        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64396.json"
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        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
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  "source_id": "core-osv",
  "document_id": 521999,
  "published_at": "2026-07-25T08:50:40.993+00:00"
}