{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-89841", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2026-89841" ], "published": "2026-09-16T10:32:03Z", "summary": "f2fs: only redirty pinned folios in redirty_blocks", "details": "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.", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:13", "name": "linux" }, "versions": [ "1:6.18.29-1+rpt1", "1:6.18.33-1+rpt1", "1:6.18.34-1+rpt1", "1:6.18.39-1+rpt1", "1:6.18.50-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.18.29+rpt-rpi-2712", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v6", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v7", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8-rt", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-2712", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v6", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v7", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8-rt", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-2712", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v6", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v7", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v8", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v8-rt", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-2712", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-v6", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-v7", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-v8", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-v8-rt", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.50+rpt-rpi-2712", "binary_version": "1:6.18.50-1+rpt1" }, { "binary_name": "linux-image-6.18.50+rpt-rpi-v6", "binary_version": "1:6.18.50-1+rpt1" }, { "binary_name": "linux-image-6.18.50+rpt-rpi-v7", "binary_version": "1:6.18.50-1+rpt1" }, { "binary_name": "linux-image-6.18.50+rpt-rpi-v8", "binary_version": "1:6.18.50-1+rpt1" }, { "binary_name": "linux-image-6.18.50+rpt-rpi-v8-rt", "binary_version": "1:6.18.50-1+rpt1" } ] }, "database_specific": { "per_version": { "1:6.18.29-1+rpt1": { "linux_commit": "66318c5b5cd8145a662303af12ed39ac07eb27cc", "upstream_version": "6.18.29", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.51" }, "1:6.18.33-1+rpt1": { "linux_commit": "95b85bebbedcaedfa7ca79116ed38b7376fba412", "upstream_version": "6.18.33", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.51" }, "1:6.18.34-1+rpt1": { "linux_commit": "c8c7494100e99ee05b11aaa4f0588a223a63d1af", "upstream_version": "6.18.34", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.51" }, "1:6.18.39-1+rpt1": { "linux_commit": "60ea684a8ace97bb0db1a16e20753bdd6ab371ff", "upstream_version": "6.18.39", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.51" }, "1:6.18.50-1+rpt1": { "linux_commit": "cff533aec2fa601846766b32ff57204e0a61bed7", "upstream_version": "6.18.50", "assessment": "commit ancestry (strak rule)", "upstream_fixed": "6.18.51" } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-89841" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/445e4a1e6025ecd5312e9a95c1b234192c976ca1" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/89c65ec3c18903de763cf567c96ab3ef60e5f3b0" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/85171332742e741ccd6f401c69b6e0d698119e72" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-09-16T14:40:32Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.8, "cvss_v3_severity": "High", "scenario": "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'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." } } }