CVE-2026-89485

Published: September 15, 2026Last modified: September 15, 2026

Description

In the Linux kernel, the following vulnerability has been resolved: lockd: pin next file across nlm_inspect_file lock-drop nlm_traverse_files() pins the current file with f_count++ across a mutex_unlock for nlm_inspect_file(), but nothing pins the saved next pointer. A concurrent nlm_release_file() can kfree the next file during the unlock window, and the iterator dereferences freed memory on the next loop step. Pin both current and next before the lock-drop. Advance by swapping the pinned cursors at the end of each iteration so next is always held alive across the unlock. Always call nlm_file_release() after dropping the iteration pin, regardless of whether the file matched the predicate. Use nlm_file_inuse(), which does a live walk of the inode lock list, rather than the cached f_locks field, so skipped files that never ran nlm_inspect_file() are evaluated correctly. Because every file in a hash bucket is now pinned and released, files skipped by the is_failover_file predicate that have no locks, blocks, shares, or external references are deleted during traversal. The old code never evaluated skipped files for cleanup. The new behavior is intentional: such files are stale and should not persist in the table.

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References

• https://git.kernel.org/stable/c/41f0a6d31615fcae261bf28a0aa50050dc93a401
• https://git.kernel.org/stable/c/526c49cff3f72c3ec74752016380c7567040581b
• https://git.kernel.org/stable/c/c24bdb7df2f34bdc38ca8a73796f5acb40f1830c
• https://git.kernel.org/stable/c/e999a88133654c6dfc68487fb49da5f20dfa2d4f