ksmbd: fix use-after-free and NULL deref in smb_grant_oplock()

{
  "id": "1841b11335f14ec7df4c726276911f9bb606c336545cd94a5480c6bc1d341348",
  "url": "https://osv.dev/vulnerability/CVE-2026-31444",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ksmbd: fix use-after-free and NULL deref in smb_grant_oplock()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free and NULL deref in smb_grant_oplock() smb_grant_oplock() has two issues in the oplock publication sequence: 1) opinfo is linked into ci->m_op_list (via opinfo_add) before add_lease_global_list() is called. If add_lease_global_list() fails (kmalloc returns NULL), the error path frees the opinfo via __free_opinfo() while it is still linked in ci->m_op_list. Concurrent m_op_list readers (opinfo_get_list, or direct iteration in smb_break_all_levII_oplock) dereference the freed node. 2) opinfo->o_fp is assigned after add_lease_global_list() publishes the opinfo on the global lease list. A concurrent find_same_lease_key() can walk the lease list and dereference opinfo->o_fp->f_ci while o_fp is still NULL. Fix by restructuring the publication sequence to eliminate post-publish failure: - Set opinfo->o_fp before any list publication (fixes NULL deref). - Preallocate lease_table via alloc_lease_table() before opinfo_add() so add_lease_global_list() becomes infallible after publication. - Keep the original m_op_list publication order (opinfo_add before lease list) so concurrent opens via same_client_has_lease() and opinfo_get_list() still see the in-flight grant. - Use opinfo_put() instead of __free_opinfo() on err_out so that the RCU-deferred free path is used. This also requires splitting add_lease_global_list() to take a preallocated lease_table and changing its return type from int to void,",
    "evidence": "osv:CVE-2026-31444",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
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            "evidence": "/affected/1/ranges"
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          {
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            "evidence": "/affected/1/ranges"
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        "affected_versions": []
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    "severity": "critical",
    "structured": {
      "id": "CVE-2026-31444",
      "aliases": [
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      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
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      "modified": "2026-10-28T02:30:25.984303542Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/48623ec358c1c600fa1e38368746f933e0f1a617",
        "https://git.kernel.org/stable/c/6d7e5a918c1d0aad06db0e17677b66fc9a471021",
        "https://git.kernel.org/stable/c/7de55bba69cbf0f9280daaea385daf08bc076121",
        "https://git.kernel.org/stable/c/9e785f004cbc56390479b77375726ea9b0d1a8a6",
        "https://git.kernel.org/stable/c/a5c6f6d6ceefed2d5210ee420fb75f8362461f46",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31444.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-31444",
        "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/2026/31xxx/CVE-2026-31444.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-31444",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 492263,
  "published_at": "2026-04-22T13:53:41.351+00:00"
}