CVE-2026-89646
CVE-2026-89646 is a security vulnerability. O3 Security confirms whether CVE-2026-89646 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
In the Linux kernel, the following vulnerability has been resolved: ceph: fix leaked inode reference on writeback abort at umount ceph_dirty_folio() takes a wrbuffer claim on each…
Description
In the Linux kernel, the following vulnerability has been resolved:
ceph: fix leaked inode reference on writeback abort at umount
ceph_dirty_folio() takes a wrbuffer claim on each newly dirtied folio: it bumps i_wrbuffer_ref (taking an ihold() on the 0->1 transition) and attaches the snap_context to folio->private. That claim is released only by ceph_put_wrbuffer_cap_refs(), which for a submitted write runs from writepages_finish().
In ceph_submit_write(), if ceph_inc_osd_stopping_blocker() fails -- which happens during umount -- the request is aborted before submission: the already-collected folios are only redirtied and unlocked, so writepages_finish() never runs and the claim is leaked. redirty_page_for_writepage() -> folio_redirty_for_writepage() -> filemap_dirty_folio() sets PG_dirty directly and does not go through ->dirty_folio, so ceph_dirty_folio() is not re-entered to rebalance it. Because every subsequent writeback also fails the osd_stopping_blocker, i_wrbuffer_ref never returns to 0, the ihold() is never dropped, and the inode cannot be evicted:
VFS: Busy inodes after unmount of ceph kernel BUG at fs/super.c:650!
Release the orphaned claim in the abort path before redirtying, via ceph_undo_wrbuffer_claim(): detach the snap_context, drop the wrbuffer reference (letting i_wrbuffer_ref reach 0 and iput() the inode), and drop the snap_context reference -- i.e. do what writepages_finish() would have done for these never-submitted folios.
Only the locked_pages entries are undone; folios still in the fbatch were never dirty-cleared by this call (folio_clear_dirty_for_io() is the ownership-transfer point, and a successful move NULLs the fbatch slot), so they hold no claim this call owns.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-89646 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-89646 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-89646. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-89646 in your dependencies?
O3 detects CVE-2026-89646 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.