ksmbd: remove stale channels from all sessions on teardown

{
  "id": "83b1716977ce013806cf8a5492666a470c6bf9e377a99bdb585877ca23b05ee1",
  "url": "https://osv.dev/vulnerability/CVE-2026-98870",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ksmbd: remove stale channels from all sessions on teardown",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: ksmbd: remove stale channels from all sessions on teardown ksmbd_sessions_deregister() removes a connection's channels from other sessions' channel lists only while conn->binding is still set: if (conn->binding) { hash_for_each_safe(sessions_table, ...) ksmbd_chann_del(conn, sess); } conn->binding is a transient flag: it is cleared once a binding SESSION_SETUP completes, and also by a subsequent non-binding SESSION_SETUP on the same connection (a reauthentication on a bound channel, or a new SessionId==0 setup). A connection that has bound a channel into another session's ksmbd_chann_list and then clears conn->binding leaves that channel behind when it disconnects: the channel, whose chann->conn points at the now freed struct ksmbd_conn, stays on the owner session's list. When the owning connection later tears down, the second loop dereferences the stale channel: xa_for_each(&sess->ksmbd_chann_list, chann_id, chann) if (chann->conn != conn) ksmbd_conn_set_exiting(chann->conn); /* freed */ which is a use-after-free write into the freed ksmbd_conn (the same stale channel is also walked by show_proc_session() through /proc). The session is leaked as well, because its channel list never empties. Remove the conn->binding gate so a connection always removes its channels from every session on teardown.",
    "evidence": "osv:CVE-2026-98870",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-98870",
      "aliases": [
        "CVE-2026-98870"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
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          "versions": [
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-98870.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:51.000389926Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/9cd6d714d3ca0cff296542dc989696884e41970f",
        "https://git.kernel.org/stable/c/a15cae16f4432a5ad919ee633e31b07178492955",
        "https://git.kernel.org/stable/c/b10665730fbf6b5e45fe422badcbbc3f0df96ef5",
        "https://git.kernel.org/stable/c/b145f9b56c87f9c23ad5464ab0844dbc1de12b36",
        "https://git.kernel.org/stable/c/f8200bb4994e65a2e5c5b314789eeae39078619d",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98870.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98870",
        "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/2026/98xxx/CVE-2026-98870.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-98870",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 519570,
  "published_at": "2026-10-23T11:37:07.113+00:00"
}