Directory Lock Bypass in Linux Kernel - Affects Multiple Platforms

CVE-2026-99084

What is CVE-2026-99084?

A vulnerability exists in the Linux kernel related to directory handling. The iterate_dir() function fails to apply necessary locking mechanisms on immutable directories, allowing a reader to hold a lock indefinitely. This can halt other processes attempting to modify or access the directory, particularly affecting instances of nullfs which are critical in various mount namespaces. The issue arises when a directory has no entries, permitting a user to create situations where other operations, such as mkdir(), cannot proceed until the reader relinquishes the lock. Implementing FOP_IMMUTABLE for immutable directories would allow iterate_dir() to bypass the lock entirely, thus enhancing overall system performance and security.

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