CVE-2026-89841 (GCVE-0-2026-89841)

Vulnerability from cvelistv5 – Published: 2026-09-16 10:31 – Updated: 2026-10-19 08:53
VLAI
Title
f2fs: only redirty pinned folios in redirty_blocks
Summary
In the Linux kernel, the following vulnerability has been resolved: f2fs: only redirty pinned folios in redirty_blocks redirty_blocks() pins folios with read_cache_folio() and then walks the same range again with filemap_lock_folio() to redirty them and drop the references it took. Commit 5951fee46bef ("f2fs: Use a folio in redirty_blocks()") changed the second pass to a do/while loop. If read_cache_folio() fails before anything is pinned, page_idx does not advance but the cleanup loop still runs once. If readahead has already populated the failed folio in page cache, that extra iteration finds it and folio_put_refs(folio, 2) drops one reference too many. Later drop_caches or reclaim can then report "BUG: Bad page state". Only redirty the range that was pinned successfully.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6639 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 5951fee46befbf6176c86482432f4f76e522f16c , < 445e4a1e6025ecd5312e9a95c1b234192c976ca1 (git)
Affected: 5951fee46befbf6176c86482432f4f76e522f16c , < 89c65ec3c18903de763cf567c96ab3ef60e5f3b0 (git)
Affected: 5951fee46befbf6176c86482432f4f76e522f16c , < 85171332742e741ccd6f401c69b6e0d698119e72 (git)
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Linux Linux Affected: 6.16
Unaffected: 0 , < 6.16 (semver)
Unaffected: 6.18.51 , ≤ 6.18.* (semver)
Unaffected: 7.2.5 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: only redirty pinned folios in redirty_blocks\n\nredirty_blocks() pins folios with read_cache_folio() and then walks the\nsame range again with filemap_lock_folio() to redirty them and drop the\nreferences it took.\n\nCommit 5951fee46bef (\"f2fs: Use a folio in redirty_blocks()\") changed\nthe second pass to a do/while loop. If read_cache_folio() fails before\nanything is pinned, page_idx does not advance but the cleanup loop still\nruns once.\n\nIf readahead has already populated the failed folio in page cache, that\nextra iteration finds it and folio_put_refs(folio, 2) drops one\nreference too many. Later drop_caches or reclaim can then report\n\"BUG: Bad page state\".\n\nOnly redirty the range that was pinned successfully."
        }
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      "metrics": [
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
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          "scenarios": [
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              "lang": "en",
              "value": "AV:L - redirty_blocks() is reached only via local F2FS_IOC_COMPRESS_FILE/F2FS_IOC_DECOMPRESS_FILE ioctls (f2fs_ioctl \u2192 f2fs_ioc_{compress,decompress}_file) on a mounted f2fs file; these are not network, Bluetooth, or USB protocol handlers.\nAC:L - The attacker drives the ioctl and can force the first read_cache_folio() to fail (memcg/ENOMEM, or a fatal signal during the killable wait after readahead inserted the folio), so the do/while cleanup always runs once; no victim-timed race or layout outside their control is required.\nPR:L - Neither ioctl checks capable()/CAP_SYS_ADMIN; they need only a writable fd (FMODE_WRITE) of a compression-enabled file, and owners can set FS_COMPR_FL via FS_IOC_SETFLAGS/chattr +c on Android/embedded f2fs userdata with compress_mode=user.\nUI:N - On typical f2fs deployments (Android userdata already mounted with compression/compress_mode=user) the attacker creates or opens their own file and issues the ioctl with no victim mount, open, or other action.\nS:U - Page-cache refcount underflow and the resulting kernel oops stay inside the host kernel\u0027s security authority; this is not a VM guest-to-host escape, IOMMU bypass, or sandbox breakout.\nC:H - The extra folio_put_refs(folio, 2) drops the page-cache reference and can free a folio still indexed in mapping-\u003ei_pages; that use-after-free of page-cache memory is a read primitive for arbitrary kernel/user data.\nI:H - The same underflow lets the freed folio be reused while still in the mapping (the stray pass also dirties and unlocks it), yielding a write primitive usable for control-flow hijack.\nA:H - If the folio is absent, filemap_lock_folio() returns ERR_PTR(-ENOENT) and production f2fs_bug_on() WARNs then dereferences it (oops); the extra-put path reports BUG: Bad page state on reclaim/drop_caches and can panic."
            }
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      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:53:34.362Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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      "title": "f2fs: only redirty pinned folios in redirty_blocks",
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    "cveId": "CVE-2026-89841",
    "datePublished": "2026-09-16T10:31:15.578Z",
    "dateReserved": "2026-09-11T19:38:34.770Z",
    "dateUpdated": "2026-10-19T08:53:34.362Z",
    "state": "PUBLISHED"
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      "version": "2"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: only redirty pinned folios in redirty_blocks\n\nredirty_blocks() pins folios with read_cache_folio() and then walks the\nsame range again with filemap_lock_folio() to redirty them and drop the\nreferences it took.\n\nCommit 5951fee46bef (\"f2fs: Use a folio in redirty_blocks()\") changed\nthe second pass to a do/while loop. If read_cache_folio() fails before\nanything is pinned, page_idx does not advance but the cleanup loop still\nruns once.\n\nIf readahead has already populated the failed folio in page cache, that\nextra iteration finds it and folio_put_refs(folio, 2) drops one\nreference too many. Later drop_caches or reclaim can then report\n\"BUG: Bad page state\".\n\nOnly redirty the range that was pinned successfully."
          }
        ],
        "id": "CVE-2026-89841",
        "lastModified": "2026-10-19T09:18:28.030",
        "metrics": {
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                "confidentialityImpact": "HIGH",
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        "vulnStatus": "Received"
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      "cve": "CVE-2026-89841",
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      "product_status:known_not_affected": "203",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: f2fs: only redirty pinned folios in redirty_blocks",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89841.json",
      "version": "3"
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}



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