{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89841", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.770Z", "datePublished": "2026-09-16T10:31:15.578Z", "dateUpdated": "2026-10-19T08:53:34.362Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:53:34.362Z" }, "descriptions": [ { "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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - redirty_blocks() is reached only via local F2FS_IOC_COMPRESS_FILE/F2FS_IOC_DECOMPRESS_FILE ioctls (f2fs_ioctl → 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's 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->i_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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/f2fs/file.c" ], "versions": [ { "version": "5951fee46befbf6176c86482432f4f76e522f16c", "lessThan": "445e4a1e6025ecd5312e9a95c1b234192c976ca1", "status": "affected", "versionType": "git" }, { "version": "5951fee46befbf6176c86482432f4f76e522f16c", "lessThan": "89c65ec3c18903de763cf567c96ab3ef60e5f3b0", "status": "affected", "versionType": "git" }, { "version": "5951fee46befbf6176c86482432f4f76e522f16c", "lessThan": "85171332742e741ccd6f401c69b6e0d698119e72", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/f2fs/file.c" ], "versions": [ { "version": "6.16", "status": "affected" }, { "version": "0", "lessThan": "6.16", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.51", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.5", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "6.18.51" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "7.2.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.16", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/445e4a1e6025ecd5312e9a95c1b234192c976ca1" }, { "url": "https://git.kernel.org/stable/c/89c65ec3c18903de763cf567c96ab3ef60e5f3b0" }, { "url": "https://git.kernel.org/stable/c/85171332742e741ccd6f401c69b6e0d698119e72" } ], "title": "f2fs: only redirty pinned folios in redirty_blocks", "x_generator": { "engine": "bippy-1.2.0" } } } }