CVE-2026-31466 (GCVE-0-2026-31466)

Vulnerability from cvelistv5 – Published: 2026-04-22 13:53 – Updated: 2026-04-22 13:53
VLAI?
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_rmb() if the softleaf entry is migration entry in softleaf_to_folio() and softleaf_to_page(). [tujinjiang@huawei.com: update function name and comments]
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: e9b61f19858a5d6c42ce2298cf138279375d0d9b , < 426ee10711586617da869c8bb798214965337617 (git)
Affected: e9b61f19858a5d6c42ce2298cf138279375d0d9b , < f1acf5887c2bbaf998dc3fe32c72b7a8b84a3ddd (git)
Affected: e9b61f19858a5d6c42ce2298cf138279375d0d9b , < 722cfaf6b31d31123439e67b5deac6b1261a3dea (git)
Affected: e9b61f19858a5d6c42ce2298cf138279375d0d9b , < 7ddcf4a245c1c5a91fdd9698757e3d95179ffe41 (git)
Affected: e9b61f19858a5d6c42ce2298cf138279375d0d9b , < b8c49ad888892ad7b77062b9c102b799a3e9b4f8 (git)
Affected: e9b61f19858a5d6c42ce2298cf138279375d0d9b , < 7ad1997b9bc8032603df8f091761114479285769 (git)
Affected: e9b61f19858a5d6c42ce2298cf138279375d0d9b , < 8bfb8414e9f2ce6f5f2f0e3d0da52f2d132128e7 (git)
Affected: e9b61f19858a5d6c42ce2298cf138279375d0d9b , < 4c5e7f0fcd592801c9cc18f29f80fbee84eb8669 (git)
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    Linux Linux Affected: 4.5
Unaffected: 0 , < 4.5 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.168 , ≤ 6.1.* (semver)
Unaffected: 6.6.134 , ≤ 6.6.* (semver)
Unaffected: 6.12.81 , ≤ 6.12.* (semver)
Unaffected: 6.18.21 , ≤ 6.18.* (semver)
Unaffected: 6.19.11 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
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      "descriptions": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/huge_memory: fix folio isn\u0027t locked in softleaf_to_folio()\n\nOn arm64 server, we found folio that get from migration entry isn\u0027t locked\nin softleaf_to_folio().  This issue triggers when mTHP splitting and\nzap_nonpresent_ptes() races, and the root cause is lack of memory barrier\nin softleaf_to_folio().  The race is as follows:\n\n\tCPU0                                             CPU1\n\ndeferred_split_scan()                              zap_nonpresent_ptes()\n  lock folio\n  split_folio()\n    unmap_folio()\n      change ptes to migration entries\n    __split_folio_to_order()                         softleaf_to_folio()\n      set flags(including PG_locked) for tail pages    folio = pfn_folio(softleaf_to_pfn(entry))\n      smp_wmb()                                        VM_WARN_ON_ONCE(!folio_test_locked(folio))\n      prep_compound_page() for tail pages\n\nIn __split_folio_to_order(), smp_wmb() guarantees page flags of tail pages\nare visible before the tail page becomes non-compound.  smp_wmb() should\nbe paired with smp_rmb() in softleaf_to_folio(), which is missed.  As a\nresult, if zap_nonpresent_ptes() accesses migration entry that stores tail\npfn, softleaf_to_folio() may see the updated compound_head of tail page\nbefore page-\u003eflags.\n\nThis issue will trigger VM_WARN_ON_ONCE() in pfn_swap_entry_folio()\nbecause of the race between folio split and zap_nonpresent_ptes()\nleading to a folio incorrectly undergoing modification without a folio\nlock being held.\n\nThis is a BUG_ON() before commit 93976a20345b (\"mm: eliminate further\nswapops predicates\"), which in merged in v6.19-rc1.\n\nTo fix it, add missing smp_rmb() if the softleaf entry is migration entry\nin softleaf_to_folio() and softleaf_to_page().\n\n[tujinjiang@huawei.com: update function name and comments]"
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      "providerMetadata": {
        "dateUpdated": "2026-04-22T13:53:56.259Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        {
          "url": "https://git.kernel.org/stable/c/4c5e7f0fcd592801c9cc18f29f80fbee84eb8669"
        }
      ],
      "title": "mm/huge_memory: fix folio isn\u0027t locked in softleaf_to_folio()",
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    "cveId": "CVE-2026-31466",
    "datePublished": "2026-04-22T13:53:56.259Z",
    "dateReserved": "2026-03-09T15:48:24.097Z",
    "dateUpdated": "2026-04-22T13:53:56.259Z",
    "state": "PUBLISHED"
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      "date": "2026-04-25",
      "epss": "0.00024",
      "percentile": "0.06802"
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    "nvd": "{\"cve\":{\"id\":\"CVE-2026-31466\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-04-22T14:16:42.780\",\"lastModified\":\"2026-04-23T16:17:41.280\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nmm/huge_memory: fix folio isn\u0027t locked in softleaf_to_folio()\\n\\nOn arm64 server, we found folio that get from migration entry isn\u0027t locked\\nin softleaf_to_folio().  This issue triggers when mTHP splitting and\\nzap_nonpresent_ptes() races, and the root cause is lack of memory barrier\\nin softleaf_to_folio().  The race is as follows:\\n\\n\\tCPU0                                             CPU1\\n\\ndeferred_split_scan()                              zap_nonpresent_ptes()\\n  lock folio\\n  split_folio()\\n    unmap_folio()\\n      change ptes to migration entries\\n    __split_folio_to_order()                         softleaf_to_folio()\\n      set flags(including PG_locked) for tail pages    folio = pfn_folio(softleaf_to_pfn(entry))\\n      smp_wmb()                                        VM_WARN_ON_ONCE(!folio_test_locked(folio))\\n      prep_compound_page() for tail pages\\n\\nIn __split_folio_to_order(), smp_wmb() guarantees page flags of tail pages\\nare visible before the tail page becomes non-compound.  smp_wmb() should\\nbe paired with smp_rmb() in softleaf_to_folio(), which is missed.  As a\\nresult, if zap_nonpresent_ptes() accesses migration entry that stores tail\\npfn, softleaf_to_folio() may see the updated compound_head of tail page\\nbefore page-\u003eflags.\\n\\nThis issue will trigger VM_WARN_ON_ONCE() in pfn_swap_entry_folio()\\nbecause of the race between folio split and zap_nonpresent_ptes()\\nleading to a folio incorrectly undergoing modification without a folio\\nlock being held.\\n\\nThis is a BUG_ON() before commit 93976a20345b (\\\"mm: eliminate further\\nswapops predicates\\\"), which in merged in v6.19-rc1.\\n\\nTo fix it, add missing smp_rmb() if the softleaf entry is migration entry\\nin softleaf_to_folio() and softleaf_to_page().\\n\\n[tujinjiang@huawei.com: update function name and comments]\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/426ee10711586617da869c8bb798214965337617\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4c5e7f0fcd592801c9cc18f29f80fbee84eb8669\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/722cfaf6b31d31123439e67b5deac6b1261a3dea\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7ad1997b9bc8032603df8f091761114479285769\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/7ddcf4a245c1c5a91fdd9698757e3d95179ffe41\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/8bfb8414e9f2ce6f5f2f0e3d0da52f2d132128e7\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b8c49ad888892ad7b77062b9c102b799a3e9b4f8\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f1acf5887c2bbaf998dc3fe32c72b7a8b84a3ddd\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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