xfrm: policy: preallocate inexact bins before xfrm_hash_rebuild reinsert

{
  "id": "c5dfe5acbddd5062b8c55bf24f9c7462e4f14c118db7b411eaec42eb8bc8ed46",
  "url": "https://osv.dev/vulnerability/CVE-2026-64579",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "xfrm: policy: preallocate inexact bins before xfrm_hash_rebuild reinsert",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: xfrm: policy: preallocate inexact bins before xfrm_hash_rebuild reinsert xfrm_hash_rebuild()'s first loop preallocates the bins/chains the reinsert loop needs, so the reinsert (after hlist_del_rcu()) cannot allocate or fail. But its guard is inverted: it skips policies with prefixlen < threshold and preallocates for the rest. prefixlen < threshold is exactly when policy_hash_bysel() returns NULL and the reinsert takes the allocating xfrm_policy_inexact_insert() path. So the loop preallocates for the exact policies (which never allocate) and skips the inexact ones, whose bin/node is then allocated GFP_ATOMIC during reinsert. On failure the error path only WARN_ONCE()s and continues, leaving a poisoned bydst node; the next rebuild's hlist_del_rcu() dereferences LIST_POISON2 and takes a GPF. Reachable under memory pressure, deterministic via failslab. Invert the guard so preallocation covers exactly the reinserted policies; the reinsert then allocates nothing and cannot fail. Crash: Oops: general protection fault, probably for non-canonical address 0xfbd59c0000000024: 0000 [#1] SMP KASAN NOPTI KASAN: maybe wild-memory-access in range [0xdead...] ... Workqueue: events xfrm_hash_rebuild RIP: 0010:xfrm_hash_rebuild+0x5b3/0x1190 RAX: dead000000000122 (LIST_POISON2 + offset) ... Call Trace: hlist_del_rcu (include/linux/rculist.h:599) xfrm_hash_rebuild (net/xfrm/xfrm_policy.c:1365) process_one_work (kernel/workqueue.c",
    "evidence": "osv:CVE-2026-64579",
    "products": [
      {
        "name": {
          "value": "Kernel",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "5.10.265",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "5.15.216",
            "evidence": "/affected/1/ranges"
          },
          {
            "value": "6.1.183",
            "evidence": "/affected/1/ranges"
          },
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            "value": "6.6.148",
            "evidence": "/affected/1/ranges"
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          {
            "value": "6.12.101",
            "evidence": "/affected/1/ranges"
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            "value": "6.18.42",
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          {
            "value": "7.1.6",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-64579",
      "aliases": [
        "CVE-2026-64579"
      ],
      "affected": [
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          "ranges": [
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                  "fixed": "1cdeed9df1306f1a277e715600772640d63defa9"
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                  "fixed": "43a4d510523779891cf8eca7ffb4a086b0b5d8bf"
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                  "fixed": "d9d9cc21cc90014724a14c447e3d587be9447107"
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            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64579.json"
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        {
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              "type": "ECOSYSTEM",
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                  "introduced": "5.0.0"
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                {
                  "fixed": "5.10.265"
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          "package": {
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            "ecosystem": "Linux"
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      ],
      "modified": "2026-10-28T02:30:25.056099014Z",
      "provider": "osv",
      "references": [
        "https://git.kernel.org/stable/c/1cdeed9df1306f1a277e715600772640d63defa9",
        "https://git.kernel.org/stable/c/43a4d510523779891cf8eca7ffb4a086b0b5d8bf",
        "https://git.kernel.org/stable/c/6aa3796d18a9fda953ad76a62b57bf6c145cb9ef",
        "https://git.kernel.org/stable/c/7acc5ed2f33608a3d83b64f50a5766843b6e2485",
        "https://git.kernel.org/stable/c/94c00391a5117530188334f740ce26d3f1256190",
        "https://git.kernel.org/stable/c/d9d9cc21cc90014724a14c447e3d587be9447107",
        "https://git.kernel.org/stable/c/e48f4c3e3df35b34be719d72d737bbeaca77cf0c",
        "https://git.kernel.org/stable/c/f38f8cce2f7e79775b3db7e8a5eacda04ac908e4",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64579.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-64579",
        "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/2026/64xxx/CVE-2026-64579.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-64579",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 491332,
  "published_at": "2026-08-05T08:09:34.346+00:00"
}