KSMBD in-kernel SMB3 server gains extended directory queries and session limits in Linux 7.4

The KSMBD in-kernel SMB3 file server receives a substantial update in the Linux 7.4 kernel merge window, adding support for multiple extended directory information query classes that improve interoperability with Windows and other SMB clients. These additions include FileIdExtdDirectoryInformation, FileId64ExtdDirectoryInformation, FileId64ExtdBothDirectoryInformation, FileIdAllExtdDirectoryInformation, and FileIdAllExtdBothDirectoryInformation, which expose more file metadata through SMB2 protocol extensions.

Beyond protocol coverage, KSMBD now allows administrators to configure per-connection session limits, providing finer-grained resource control. The update also brings POSIX compatibility improvements, validation enhancements, better handling of Windows chained-compression scenarios, encryption refinements, and additional security hardening. These changes affect users running KSMBD on Linux file servers serving Windows, macOS, and other SMB clients, with the code landing now for the Linux 7.4 release cycle.

What changes in KSMBD for Linux 7.4

• Extended SMB2 directory queries: Five new information levels are now wired up: FileIdExtdDirectoryInformation, FileId64ExtdDirectoryInformation, FileId64ExtdBothDirectoryInformation, FileIdAllExtdDirectoryInformation, and FileIdAllExtdBothDirectoryInformation, expanding metadata exposure to SMB clients.
• Per-connection session limits: KSMBD adds configurable caps on sessions per connection, giving administrators a tunable to constrain resource consumption and mitigate certain denial-of-service vectors.
• POSIX improvements: Multiple POSIX compatibility enhancements are included, continuing KSMBD's effort to bridge semantic gaps between Linux filesystem behavior and SMB protocol expectations.
• Compression and encryption: Windows chained-compression compatibility is improved, and encryption handling receives refinements alongside broader security hardening changes.
• Validation hardening: Additional validation enhancements are merged, reducing attack surface and improving robustness when parsing client requests.

Why it matters

For Linux storage administrators and NAS builders, these KSMBD improvements reduce the need to run Samba in userspace for SMB3 workloads that require extended directory metadata or stricter session controls, potentially lowering overhead and simplifying deployments. The POSIX and encryption hardening also matter for organizations running mixed Linux-Windows environments where protocol fidelity and security posture are operational requirements.