{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89646", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.741Z", "datePublished": "2026-09-11T19:45:37.767Z", "dateUpdated": "2026-10-19T08:50:17.976Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:50:17.976Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nceph: fix leaked inode reference on writeback abort at umount\n\nceph_dirty_folio() takes a wrbuffer claim on each newly dirtied folio: it\nbumps i_wrbuffer_ref (taking an ihold() on the 0->1 transition) and\nattaches the snap_context to folio->private. That claim is released only\nby ceph_put_wrbuffer_cap_refs(), which for a submitted write runs from\nwritepages_finish().\n\nIn ceph_submit_write(), if ceph_inc_osd_stopping_blocker() fails -- which\nhappens during umount -- the request is aborted before submission: the\nalready-collected folios are only redirtied and unlocked, so\nwritepages_finish() never runs and the claim is leaked.\nredirty_page_for_writepage() -> folio_redirty_for_writepage() ->\nfilemap_dirty_folio() sets PG_dirty directly and does not go through\n->dirty_folio, so ceph_dirty_folio() is not re-entered to rebalance it.\nBecause every subsequent writeback also fails the osd_stopping_blocker,\ni_wrbuffer_ref never returns to 0, the ihold() is never dropped, and the\ninode cannot be evicted:\n\n VFS: Busy inodes after unmount of ceph\n kernel BUG at fs/super.c:650!\n\nRelease the orphaned claim in the abort path before redirtying, via\nceph_undo_wrbuffer_claim(): detach the snap_context, drop the wrbuffer\nreference (letting i_wrbuffer_ref reach 0 and iput() the inode), and drop\nthe snap_context reference -- i.e. do what writepages_finish() would have\ndone for these never-submitted folios.\n\nOnly the locked_pages entries are undone; folios still in the fbatch were\nnever dirty-cleared by this call (folio_clear_dirty_for_io() is the\nownership-transfer point, and a successful move NULLs the fbatch slot), so\nthey hold no claim this call owns." } ], "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 leak is in ceph_submit_write() from ceph_writepages_start() during local VFS writeback on umount (ceph_kill_sb → sync_filesystem → do_writepages), not MDS/OSD message handlers. fs/ceph is a kernel client with no network-facing server listener.\nAC:L - Dirtying pages then unmounting drives both sides: ceph_kill_sb waits at most mount_timeout (default 60s) or a killable signal, then sets STOPPING_FLUSHING while writepages_start still holds a blocker and locked folios, so the abort is reached reliably without an uncontrolled race.\nPR:L - An unprivileged user with write access to an already-mounted CephFS can dirty pages; container/pod teardown, autofs, or systemd performs the umount. CephFS lacks FS_USERNS_MOUNT, but the attacker does not need CAP_SYS_ADMIN themselves.\nUI:N - The attacker dirties files and can trigger or wait for unmount via pod exit, autofs idle unmount, or their own umount; no separate victim action such as opening a file or mounting the filesystem is required.\nS:U - The leaked inode references and subsequent superblock teardown affect only the host kernel's VFS/Ceph client state within the same security authority; this is not a VM escape, IOMMU bypass, or sandbox escape.\nC:H - The leaked ihold pins inodes through generic_shutdown_super so the superblock and ceph_fs_client are destroyed while those inodes remain. Later writeback or iput on the leftover mapping is a use-after-free of the freed superblock, scored High per UAF guidance.\nI:H - Inodes that survive umount retain address_spaces and pointers into destroyed ceph_fs_client/mdsc state. Subsequent iput_final/writeback operate on freed objects and poisoned i_op/s_op, a UAF write and control-flow primitive scored High.\nA:H - Unmount reports \"VFS: Busy inodes after unmount of ceph\" and hits CHECK_DATA_CORRUPTION in generic_shutdown_super (BUG() with CONFIG_BUG_ON_DATA_CORRUPTION), and VFS_PTR_POISON on surviving inodes guarantees a later oops or panic." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/ceph/addr.c" ], "versions": [ { "version": "fd7449d937e7fb3144770592927cf452bf66dbd3", "lessThan": "ec32015a955c5d326c5e26610edfdcccd52f2314", "status": "affected", "versionType": "git" }, { "version": "fd7449d937e7fb3144770592927cf452bf66dbd3", "lessThan": "ac7a5a5385762df458d10cccc086a4e079be7409", "status": "affected", "versionType": "git" }, { "version": "fd7449d937e7fb3144770592927cf452bf66dbd3", "lessThan": "c25aee9c630fb86f98d79eccb75765067079b972", "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/ceph/addr.c" ], "versions": [ { "version": "6.15", "status": "affected" }, { "version": "0", "lessThan": "6.15", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.50", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "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": "6.15", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/ec32015a955c5d326c5e26610edfdcccd52f2314" }, { "url": "https://git.kernel.org/stable/c/ac7a5a5385762df458d10cccc086a4e079be7409" }, { "url": "https://git.kernel.org/stable/c/c25aee9c630fb86f98d79eccb75765067079b972" } ], "title": "ceph: fix leaked inode reference on writeback abort at umount", "x_generator": { "engine": "bippy-1.2.0" } } } }