FKIE_CVE-2026-31466

Vulnerability from fkie_nvd - Published: 2026-04-22 14:16 - Updated: 2026-05-07 18:25
Severity
4.7 (Medium) - CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
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]
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/426ee10711586617da869c8bb798214965337617Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/4c5e7f0fcd592801c9cc18f29f80fbee84eb8669Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/722cfaf6b31d31123439e67b5deac6b1261a3deaPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7ad1997b9bc8032603df8f091761114479285769Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/7ddcf4a245c1c5a91fdd9698757e3d95179ffe41Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8bfb8414e9f2ce6f5f2f0e3d0da52f2d132128e7Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/b8c49ad888892ad7b77062b9c102b799a3e9b4f8Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/f1acf5887c2bbaf998dc3fe32c72b7a8b84a3dddPatch
Impacted products
Vendor Product Version
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel *
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
To clipboard 

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  "cveTags": [],
  "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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  "id": "CVE-2026-31466",
  "lastModified": "2026-05-07T18:25:42.033",
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          "attackComplexity": "HIGH",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 4.7,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
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        "exploitabilityScore": 1.0,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
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  "published": "2026-04-22T14:16:42.780",
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}


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