mm/huge_memory: fix folio isn't locked in softleaf_to_folio()

{
  "id": "b4b82edb2440682c0d56b25a11fbfee8e27cdac4aa8df4d1f000c3dd17576a80",
  "url": "https://osv.dev/vulnerability/CVE-2026-31466",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "mm/huge_memory: fix folio isn't locked in softleaf_to_folio()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: mm/huge_memory: fix folio isn't locked in softleaf_to_folio() On arm64 server, we found folio that get from migration entry isn't locked in softleaf_to_folio(). This issue triggers when mTHP splitting and zap_nonpresent_ptes() races, and the root cause is lack of memory barrier in softleaf_to_folio(). The race is as follows: CPU0 CPU1 deferred_split_scan() zap_nonpresent_ptes() lock folio split_folio() unmap_folio() change ptes to migration entries __split_folio_to_order() softleaf_to_folio() set flags(including PG_locked) for tail pages folio = pfn_folio(softleaf_to_pfn(entry)) smp_wmb() VM_WARN_ON_ONCE(!folio_test_locked(folio)) prep_compound_page() for tail pages In __split_folio_to_order(), smp_wmb() guarantees page flags of tail pages are visible before the tail page becomes non-compound. smp_wmb() should be paired with smp_rmb() in softleaf_to_folio(), which is missed. As a result, if zap_nonpresent_ptes() accesses migration entry that stores tail pfn, softleaf_to_folio() may see the updated compound_head of tail page before page->flags. This issue will trigger VM_WARN_ON_ONCE() in pfn_swap_entry_folio() because of the race between folio split and zap_nonpresent_ptes() leading to a folio incorrectly undergoing modification without a folio lock being held. This is a BUG_ON() before commit 93976a20345b (\"mm: eliminate further swapops predicates\"), which in merged in v6.19-rc1. To fix it, add missing smp_r",
    "evidence": "osv:CVE-2026-31466",
    "products": [
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          "value": "Kernel",
          "evidence": "/affected/1/package/name"
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        "prerequisites": [],
        "fixed_versions": [
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            "value": "5.10.253",
            "evidence": "/affected/1/ranges"
          },
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            "value": "5.15.203",
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        "affected_versions": []
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "CVE-2026-31466",
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        "CVE-2026-31466"
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            "ecosystem": "Linux"
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      "modified": "2026-10-28T02:30:50.004439994Z",
      "provider": "osv",
      "references": [
        "https://cert-portal.siemens.com/productcert/html/ssa-019113.html",
        "https://cert-portal.siemens.com/productcert/html/ssa-082556.html",
        "https://cert-portal.siemens.com/productcert/html/ssa-457936.html",
        "https://git.kernel.org/stable/c/426ee10711586617da869c8bb798214965337617",
        "https://git.kernel.org/stable/c/4c5e7f0fcd592801c9cc18f29f80fbee84eb8669",
        "https://git.kernel.org/stable/c/722cfaf6b31d31123439e67b5deac6b1261a3dea",
        "https://git.kernel.org/stable/c/7ad1997b9bc8032603df8f091761114479285769",
        "https://git.kernel.org/stable/c/7ddcf4a245c1c5a91fdd9698757e3d95179ffe41",
        "https://git.kernel.org/stable/c/8bfb8414e9f2ce6f5f2f0e3d0da52f2d132128e7",
        "https://git.kernel.org/stable/c/b8c49ad888892ad7b77062b9c102b799a3e9b4f8",
        "https://git.kernel.org/stable/c/f1acf5887c2bbaf998dc3fe32c72b7a8b84a3ddd",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31466.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-31466",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
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        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": null
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  "source_id": "core-osv",
  "document_id": 518189,
  "published_at": "2026-04-22T13:53:56.259+00:00"
}