CVE-2026-52990: fsnotify: fix inode reference leak in fsnotify_recalc_mask()

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-06-24 · updated 2026-10-30

Description

In the Linux kernel, the following vulnerability has been resolved: fsnotify: fix inode reference leak in fsnotify_recalc_mask() fsnotify_recalc_mask() fails to handle the return value of __fsnotify_recalc_mask(), which may return an inode pointer that needs to be released via fsnotify_drop_object() when the connector's HAS_IREF 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 fsnotify_sb_delete generic_shutdown_super kill_anon_super cleanup_mnt task_work_run do_exit do_group_exit The race window that triggers the iref leak: Thread A (adding mark) Thread B (removing mark) ────────────────────── ──────────────────────── fsnotify_add_mark_locked(): fsnotify_add_mark_list(): spin_lock(conn->lock) add mark_B(evictable) to list spin_unlock(conn->lock) return /* ---- gap: no lock held ---- */ fsnotify_detach_mark(mark_A): spin_lock(mark_A->lock) clear ATTACHED flag on mark_A spin_unlock(mark_A->lock) fsnotify_put_mark(mark_A) fsnotify_recalc_mask(): spin_lock(conn->lock) __fsnotify_recalc_mask(): /* mark_A skipped: ATTACHED cleared */ /* only mark_B(evictable) remains */ want_iref = false has_iref = true /* not yet cleared */ -> HAS_IREF transitions true -> false -> returns inode pointer spin_unlock(conn->lock) /* BUG: return value discarded! * iput() and fsnotify_put_sb_watched_objects() * are never called */ Fix this by deferring the transition true -> false of HAS_IREF flag from fsnotify_recalc_mask() (Thread A) to fsnotify_put_mark() (thread B).

Affected products

Linux kernel: from 5.10.220 before 5.11; from 5.15.154 before 5.16; from 5.19 before 6.12.91; from 6.13 before 6.18.33; from 6.19 before 7.0.10; 7.1-rc1 — fixed in 5.11, 5.16, 6.12.91, 6.18.33, 7.0.10
Linux: from 5.10.220 before 5.11; from 5.15.154 before 5.16 — fixed in 5.11, 5.16

How to fix

Upgrade to a fixed version: Linux kernel 5.11, 5.16, 6.12.91, 6.18.33; Linux 5.11, 5.16. Check the vendor advisory for mitigations.

References

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