{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89836", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.769Z", "datePublished": "2026-09-16T10:31:10.233Z", "dateUpdated": "2026-10-19T08:53:29.553Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:53:29.553Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: fix folio_nr_pages() race after put in large folio invalidate\n\nOur v6.18 based Android system is continuely suffering livelock and bad\npage stat as shown in[1] which related to broken xarray slot status. By\ninvestigating big folio operations within f2fs, we find below races and\nfix it by get the nr_pages before drop the refcount and folio_lock.\n\nf2fs_get_read_data_folio() calls f2fs_folio_put() before\nfolio_nr_pages() when invalidating a large folio from the page cache.\nThat unlocks the folio and drops the caller reference, leaving a window\nwhere a concurrent truncate or folio split can shrink the compound folio\nor free it before the invalidate range is computed. An undersized range\nthen leaves split sub-folios in mapping->i_pages, which can later\ninteract badly with truncate and reclaim (stale xarray entries and bad\npage state when folio->mapping no longer matches the mapping being\ntruncated).\n\n[1]\nPID: 2594 TASK: ffffff8169b81580 CPU: 7 COMMAND: \"Thread-3\"\n #0 [ffffffc08ef2b8a0] xas_load at ffffffe52d1f42a4\n #1 [ffffffc08ef2b900] find_get_entries at ffffffe52c185798\n #2 [ffffffc08ef2bb60] truncate_inode_pages_range at ffffffe52c19e83c\n #3 [ffffffc08ef2bbc0] truncate_inode_pages_final at ffffffe52c19ec2c\n #4 [ffffffc08ef2bc20] f2fs_evict_inode at ffffffe52c4c8400\n #5 [ffffffc08ef2bcc0] evict at ffffffe52c2de9f4\n #6 [ffffffc08ef2bd00] iput at ffffffe52c2db1b4\n #7 [ffffffc08ef2bd30] dentry_unlink_inode at ffffffe52c2d7204\n #8 [ffffffc08ef2bd50] __dentry_kill at ffffffe52c2d3dcc\n #9 [ffffffc08ef2bd80] dput at ffffffe52c2d3c3c\n #10 [ffffffc08ef2bda0] __fput at ffffffe52c2b0a7c\n #11 [ffffffc08ef2bde0] ____fput at ffffffe52c2b1034\n #12 [ffffffc08ef2bdf0] task_work_run at ffffffe52beea200\n #13 [ffffffc08ef2be20] exit_to_user_mode_loop at ffffffe52bfbc17c\n #14 [ffffffc08ef2be80] el0_svc at ffffffe52d1f8e54\n #15 [ffffffc08ef2beb0] el0t_64_sync_handler at ffffffe52d1f8d10" } ], "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 - The bug is in f2fs_get_read_data_folio() on a locally mounted f2fs volume, reached when GC or other f2fs helpers grab a single-page folio while a large folio is cached. f2fs is the Android/embedded userdata filesystem; the path is local syscalls, not a network protocol.\nAC:L - The attacker drives both sides of the race: one thread keeps large folios cached and forces GC via writes into f2fs_balance_fs, while concurrent threads split or reclaim those folios with posix_fadvise(DONTNEED), madvise, or memory pressure in the window after f2fs_folio_put() and before folio_nr_pages().\nPR:L - CAP_LINUX_IMMUTABLE is needed only to set the flag, but Android f2fs /data already has immutable/fsverity files with large folios. An unprivileged app can read them, write its own data to trigger GC without CAP_SYS_ADMIN, and race reclaim; the GC ioctl is optional.\nUI:N - The attacker can populate large folios, force GC, and race folio split or reclaim with their own processes; no separate victim action is required.\nS:U - Page-cache xarray corruption and folio use-after-free stay inside the host kernel; this is local privilege escalation, not a VM, IOMMU, or sandbox boundary crossing.\nC:H - After the put, folio_nr_pages() may run on a split or already-freed folio, and an undersized invalidate leaves stale i_pages xarray entries. That page-cache UAF allows a reused folio to be read as another mapping's pages, enabling kernel memory disclosure.\nI:H - Stale mapping->i_pages slots and UAF of compound-folio metadata are heap and page-cache corruption. Reused folios and later truncate or reclaim against the wrong mapping yield write primitives and control-flow hijacking, not only a crash.\nA:H - The reported failure is livelock and bad page state in truncate_inode_pages_range (xas_load/find_get_entries) during inode eviction, i.e. a kernel oops, BUG, or hang with complete loss of availability." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/f2fs/data.c" ], "versions": [ { "version": "05e65c14ea59a401cec4284e9d612f9d5dc1b3f8", "lessThan": "cc34df18da92f68f9b384c3ae95ad64be46cb5ee", "status": "affected", "versionType": "git" }, { "version": "05e65c14ea59a401cec4284e9d612f9d5dc1b3f8", "lessThan": "0dab71381f1b4d12dc2056f8bd5aaa9d93ce9082", "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/data.c" ], "versions": [ { "version": "7.0", "status": "affected" }, { "version": "0", "lessThan": "7.0", "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": "7.0", "versionEndExcluding": "7.2.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/cc34df18da92f68f9b384c3ae95ad64be46cb5ee" }, { "url": "https://git.kernel.org/stable/c/0dab71381f1b4d12dc2056f8bd5aaa9d93ce9082" } ], "title": "f2fs: fix folio_nr_pages() race after put in large folio invalidate", "x_generator": { "engine": "bippy-1.2.0" } } } }