GHSA-3XRV-9P49-WQM3

Vulnerability from github – Published: 2026-10-18 18:31 – Updated: 2026-10-18 18:31
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

net/sched: cls_u32: fix manual hash table handle IDR aliasing

A u32 hash table created with an explicit handle ('tc filter add ... handle 801: u32 divisor N') keys its IDR entry on the raw handle, while the destroy paths free it under handle2id(handle). The two key domains disagree for handles in the 0x800..0xFFF htid range: handle2id() folds them back into the auto-allocated id space (1..0x7FF).

A manual table therefore leaves its raw-keyed IDR entry unreachable on delete (a permanent leak), and its delete can drop the idr entry of an unrelated live auto table. A later auto allocation can then hand out a handle that aliases the live manual table; u32_lookup_ht() first-match routes lookups and TCA_U32_LINK for that htid to the wrong table.

Key the divisor-path alloc on handle2id(handle) so allocation and removal share one key domain. A manual handle that maps onto an id already in use is rejected with -ENOSPC, and auto allocation skips ids held by live manual tables.

Conditions to recreate: ip link add test0 type dummy tc qdisc add dev test0 clsact tc filter add dev test0 ingress protocol ip pref 1 \ handle 801: u32 divisor 16 tc filter add dev test0 ingress protocol ip pref 2 u32 divisor 16 tc -d filter show dev test0 ingress | grep 'fh 801:' # unpatched: two live tables with handle 0x80100000 (the pref 2 root # hnode is auto-allocated id 1); patched: the auto hnode takes id 2.

Also tested with a poc with a live u32 table on the block, add/delete a manual table 'handle 901: u32 divisor 1' twice; unpatched, the re-add fails with -ENOSPC because the raw key leaked on the first delete.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98629"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-18T16:17:15Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: cls_u32: fix manual hash table handle IDR aliasing\n\nA u32 hash table created with an explicit handle (\u0027tc filter add ...\nhandle 801: u32 divisor N\u0027) keys its IDR entry on the raw handle, while\nthe destroy paths free it under handle2id(handle). The two key domains\ndisagree for handles in the 0x800..0xFFF htid range:\nhandle2id() folds them back into the auto-allocated id space (1..0x7FF).\n\nA manual table therefore leaves its raw-keyed IDR entry unreachable on\ndelete (a permanent leak), and its delete can drop the idr entry of an\nunrelated live auto table. A later auto allocation can then hand out a\nhandle that aliases the live manual table; u32_lookup_ht() first-match\nroutes lookups and TCA_U32_LINK for that htid to the wrong table.\n\nKey the divisor-path alloc on handle2id(handle) so allocation and\nremoval share one key domain. A manual handle that maps onto an id\nalready in use is rejected with -ENOSPC, and auto allocation skips ids\nheld by live manual tables.\n\nConditions to recreate:\n  ip link add test0 type dummy\n  tc qdisc add dev test0 clsact\n  tc filter add dev test0 ingress protocol ip pref 1 \\\n          handle 801: u32 divisor 16\n  tc filter add dev test0 ingress protocol ip pref 2 u32 divisor 16\n  tc -d filter show dev test0 ingress | grep \u0027fh 801:\u0027\n  # unpatched: two live tables with handle 0x80100000 (the pref 2 root\n  # hnode is auto-allocated id 1); patched: the auto hnode takes id 2.\n\nAlso tested with a poc with a live u32 table on the block, add/delete a manual\ntable \u0027handle 901: u32 divisor 1\u0027 twice; unpatched, the re-add fails with\n-ENOSPC because the raw key leaked on the first delete.",
  "id": "GHSA-3xrv-9p49-wqm3",
  "modified": "2026-10-18T18:31:57Z",
  "published": "2026-10-18T18:31:57Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98629"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0a5f5d9e94dead312d32c366b917c64e552b72f7"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/0fac292d93fdb313099e98cce928b3a524c92c94"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/21fc07924e996e1e661268ca269c86b8d59d25b3"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/2f898f9ec7c73c5697ee462681e7ea6984ee1f3d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/54a454c5e41f5e2cb70c8163140ce095c5d5eefd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f6696481eedfd5752b4b56eed715d0b0fe48b9c5"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}



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