net/sched: cls_u32: fix duplicate handle when node ID pool is exhausted

{
  "id": "e98df6fbec55840a5de9046228bb93ed09b6aaf5e5095839e8f4c0aa0f4fb0ab",
  "url": "https://osv.dev/vulnerability/CVE-2026-98104",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "net/sched: cls_u32: fix duplicate handle when node ID pool is exhausted",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: net/sched: cls_u32: fix duplicate handle when node ID pool is exhausted gen_new_kid() falls back to returning max (htid | 0xFFF) when both idr_alloc_u32() ranges are full, instead of reporting an error. u32_change() trusts that value and inserts a new knode with a handle that is already live in the hash table, breaking handle uniqueness within the table's node ID space. The handle was never reserved in ht->handle_idr, so every later error path that does idr_remove(&ht->handle_idr, handle) removes the reservation of a different, live knode, which is then reused — one failed add compounds into further duplicates. The 4095 limit is per (table, bucket) — ht->handle_idr is per hash table and the range is derived from htid (bucketid), so a table with divisor 256 can legitimately hold 256*4095 knodes. The sibling helper gen_new_htid() has the same silent in-band failure: it returns 0 when the tp_c handle pool (1..0x7FF) is full, and u32_init() publishes the root hash table with handle 0 without checking. Two root tables with handle 0 alias in u32_lookup_ht(), allowing cross-tcf_proto knode add/lookup/delete. Add the same exhaustion check that the divisor path already has. Return an error so u32_change() fails with ENOSPC/ENOMEM when the node ID space is exhausted, and so u32_init() fails with -ENOMEM when the hash table ID space is exhausted. The extack message distinguishes pool exhaustion (-ENOSPC) from a transien",
    "evidence": "osv:CVE-2026-98104",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "6.1.189",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.6.158",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.12.111",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.18.53",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "7.2.7",
            "evidence": "/affected/1/ranges"
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        "affected_versions": []
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    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-98104",
      "aliases": [
        "CVE-2026-98104"
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      "affected": [
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            "ecosystem": "Linux"
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      ],
      "modified": "2026-10-28T02:30:25.894367664Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/6890e28840bae4f6805e8de981c4ec8e12a4e064",
        "https://git.kernel.org/stable/c/84223baf21bc9b008444ae9bc38d5fb91fe00b9d",
        "https://git.kernel.org/stable/c/d7e7e98d23f42a92d9ab7e36302bd96bd9b33b5f",
        "https://git.kernel.org/stable/c/f4ee13ed7f7b22dcd8287fcf477ae37bd84567da",
        "https://git.kernel.org/stable/c/f594f04268d01c5fdc975f3f51fc219ea2159ac6",
        "https://git.kernel.org/stable/c/feab9261b537df4ebb8350e4779bc185373059fd",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98104.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98104",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
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    "related_cves": [
      {
        "value": "CVE-2026-98104",
        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 492593,
  "published_at": "2026-09-25T10:35:54.544+00:00"
}