CVE-2026-52990: fsnotify: fix inode reference leak in fsnotify_recalc_mask()
In the Linux kernel, the following vulnerability has been resolved:
fsnotify: fix inode reference leak in fsnotifyrecalcmask()
fsnotifyrecalcmask() fails to handle the return value of fsnotifyrecalcmask(), which may return an inode pointer that needs to be released via fsnotifydropobject() when the connector's HASIREF flag transitions from set to cleared.
This manifests as a hung task with the following call trace:
INFO: task umount:1234 blocked for more than 120 seconds. Call Trace: schedule schedule fsnotifysbdelete genericshutdownsuper killanonsuper cleanupmnt taskworkrun doexit dogroupexit
The race window that triggers the iref leak:
Thread A (adding mark) Thread B (removing mark) ────────────────────── ──────────────────────── fsnotifyaddmarklocked(): fsnotifyaddmarklist(): spinlock(conn->lock) add markB(evictable) to list spinunlock(conn->lock) return
/ ---- gap: no lock held ---- /
fsnotifydetachmark(markA): spinlock(markA->lock) clear ATTACHED flag on markA spinunlock(markA->lock) fsnotifyputmark(markA)
fsnotifyrecalcmask(): spinlock(conn->lock) fsnotifyrecalcmask(): / markA skipped: ATTACHED cleared / / only markB(evictable) remains / wantiref = false hasiref = true / not yet cleared / -> HASIREF transitions true -> false -> returns inode pointer spinunlock(conn->lock) / BUG: return value discarded! iput() and fsnotifyputsbwatchedobjects() are never called /
Fix this by deferring the transition true -> false of HASIREF flag from fsnotifyrecalcmask() (Thread A) to fsnotifyputmark() (thread B).
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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Defer the transition of the connector's HAS_IREF flag from true to false from fsnotify_recalc_mask() (Thread A) to fsnotify_put_mark() (Thread B), ensuring the inode pointer returned by __fsnotify_recalc_mask() is released via fsnotify_drop_object().
Event History
Frequently Asked Questions
What impact can this issue have on an affected system?
The inode reference leak can leave an unmount task blocked for more than 120 seconds. The stated CVSS vector indicates a local, low-privileged attacker can cause an availability impact without user interaction.
What conditions are needed to trigger the leak?
The issue requires a race between adding an evictable fsnotify mark and removing another mark. During that race, the connector's HAS_IREF state can transition from set to cleared and the returned inode reference is not released.
Is a fix available?
Yes. A patch is available, with stable kernel references provided for the fix.