ksmbd_tree_conn_connect() publishes a new tree connection in
sess->tree_conns with a single reference and returns its pointer to
smb2_tree_connect(). The handler continues to initialize the object and
build the response after publication. A concurrent session logoff can
erase the connection and drop that reference, freeing the object while
the handler still uses it.

BUG: KASAN: slab-use-after-free in smb2_tree_connect+0xe3d/0xf90
  smb2_tree_connect (fs/smb/server/smb2pdu.c:2872)
  handle_ksmbd_work
  process_one_work
  worker_thread
  kthread

After xa_store() succeeds, take a second reference before releasing
tree_conns_lock. The original reference belongs to the xarray entry and
the second belongs to the creating smb2_tree_connect() handler.

Keep the references balanced in every path:

- On normal exit or an error after publication, smb2_tree_connect()
  drops its creator reference. Error cleanup also calls
  ksmbd_tree_conn_disconnect(), which drops the xarray reference only if
  it removes the exact entry.
- SMB2 TREE_DISCONNECT uses the same helper to remove the entry and drop
  its xarray reference. The request's existing lookup reference remains
  owned by the request and is released by the existing cleanup.
- Session LOGOFF removes each entry and drops its xarray reference. If
  it wins the race, later cleanup sees that the entry is gone and does
  not drop that reference again.

To enforce this ownership, claim the disconnected state and erase the
exact entry atomically under tree_conns_lock. This guarantees one drop
for the xarray reference and one drop by each in-flight user, regardless
of which teardown path wins. If logoff removes the entry before
initialization completes, fail the connect instead of marking the
detached object TREE_CONNECTED.

Fixes: 33b235a6e6eb ("ksmbd: fix race condition between tree conn lookup and disconnect")
Reported-by: Xiang Mei (Microsoft) <xmei5@asu.edu>
Cc: AutonomousCodeSecurity@microsoft.com
Cc: stable@vger.kernel.org
Signed-off-by: Cen Zhang (Microsoft Security FORGE Labs) <cenzhang@linux.microsoft.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

Validate IPC share configuration payload sizes before consuming
variable-length fields. Bound veto list parsing and account for
the separator byte when deriving the path length.

Fixes: a677ebd8ca2f ("ksmbd: validate payload size in ipc response")
Reported-by: Kanishka De Silva <kpskanna1915@gmail.com>
Reported-by: Farhad Alemi <farhad.alemi@berkeley.edu>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

SMB3 multichannel allows requests for one session to run on multiple
connections. Wait for all channels bound to a session before freeing
shared session objects.

A deferred byte-range lock remains counted as a running request and only
wakes when its file closes. Wake blocked locks during the drain without
unpublishing or modifying their file objects. Synchronous CANCEL requests
must invoke their cancellation callback to wake pending operations, while
CHANGE_NOTIFY completion remains specific to the asynchronous path.

Serialize session teardown with channel registration and previous-session
cleanup, and use atomic work-state transitions so LOGOFF, CANCEL, and
connection teardown invoke cancellation callbacks only once.

Fixes: 76e98a158b20 ("ksmbd: fix race condition between destroy_previous_session() and smb2 operations()")
Reported-by: Cheryl Babcock <cheryl@renat.io>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

Pull smb server updates from Namjae Jeon:
 "This contains server updates focused on SMB2 command sequencing, SMB3
  request replay and encryption, Apple Time Machine interoperability,
  protocol-compatibility fixes validated with smbtorture, security
  hardening, SMB Direct transport support, connection reliability, and
  other correctness improvements.

  New features:

   - Implement the SMB2 command sequence window

     Enforce the credit-based MessageId range for each connection,
     rejecting out-of-window, duplicate, and wrapped sequence numbers.
     This prevents invalid requests and same-channel replays from being
     processed

   - Add SMB3 request replay support

     SMB3 clients may resend requests with SMB2_FLAGS_REPLAY_OPERATION
     after a channel disconnect when the original response was lost.
     Track the required channel and open state to safely handle durable
     CREATE replays and make oplock, lease, and lock replays idempotent,
     avoiding duplicate state changes and improving multichannel
     reconnect reliability

   - Add opt-in Apple Time Machine support

     Implement the AAPL negotiation and related Finder, stream,
     COPYCHUNK, sparse-file, CHANGE_NOTIFY, and RPC compatibility
     required for Time Machine shares, allowing macOS backupd to use
     ksmbd for backups

   - Add per-share SMB3 encryption support

     Allow individual shares to require SMB3 encryption by advertising
     SMB2_SHAREFLAG_ENCRYPT_DATA in TREE_CONNECT responses and rejecting
     unencrypted tree connects and plaintext requests for protected
     shares

   - Add SMB Direct RDMA encryption support

     Extend SMB Direct to support SMB3 encrypted payloads over RDMA,
     with transform negotiation and encryption/decryption for RDMA
     READ/WRITE

  Other changes:

   - Parse and retain AppInstanceVersion contexts, enforce version
     ordering, close older active handles for newer takeovers, and
     reject invalid or unversioned opens according to the SMB2 semantics

   - Accept durable reconnect requests that omit VolatileFileId when the
     persistent ID and reconnect context identify the handle, while
     continuing to reject explicit volatile-ID mismatches

   - Fix SMB2/SMB3 protocol validation and security issues, including
     request offsets, file and object IDs, IPC responses, output buffer
     sizes, SMB3.1.1 binding validation, signing-required handling,
     durable handles, ACLs, maximal access, and security information

   - Fix heap out-of-bounds accesses, use-after-free bugs, memory leaks,
     invalid pointer dereferences, and sensitive-data lifetime issues in
     authentication, Kerberos, preauthentication, sessions, connections,
     and module teardown

   - Correct alternate-data-stream and named-stream handling, COPYCHUNK
     behavior, sparse-file and compression attributes, allocated-range
     queries, file trimming, duplicate extents, DOS attributes,
     snapshots, normalized names, and partial information responses

   - Fix locking, lease, oplock, durable reconnect, async request, and
     CHANGE_NOTIFY races, including deferred-lock rollback, parent
     directory lease notifications, and connection teardown lifetime
     bugs

   - Fix SMB3 encryption handling for compressed requests, expired
     encrypted sessions, interim responses, bound multichannel
     connections, and decryption failures

   - Fix SMB3 multichannel session lookup and session state transitions
     so changes are scoped to the correct bound connections and cannot
     revive connections that are already shutting down

   - Fix DACL access checks so ACE walks are bounded by the declared
     DACL size, preventing data beyond the DACL boundary from being
     interpreted during access validation

   - Fix session accounting and lifetime issues, including session
     counter updates during publication and removal, session leaks on
     registration failure, and procfs creation diagnostics

   - Improve TCP connection reliability by enabling TCP keepalive for
     accepted connections and preserving TCP timers for kernel sockets,
     preventing silent peers from holding connections indefinitely

   - Fix smbdirect RDMA cleanup ordering for completion queues, QPs,
     child sockets, and listener locking

   - Improve async response framing, multi-iovec signing, RPC pipe
     status handling, and ksmbd procfs monitoring for server, share,
     connection, session, and open-file state

   - Remove the obsolete DES crypto header and Kconfig dependency now
     that NTLMv1 support has been removed

   - Update the ksmbd repository URL in MAINTAINERS and add an
     additional KSMBD reviewer"

* tag 'ksmbd-for-7.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/linkinjeon/smb: (142 commits)
  MAINTAINERS: update ksmbd repository URL
  MAINTAINERS: add myself as KSMBD reviewer
  smb: server: remove unused DES crypto header
  smb: server: Remove obsolete "select CRYPTO_LIB_DES" from Kconfig file
  ksmbd: keep TCP timers alive for kernel sockets
  ksmbd: enable TCP keepalive for accepted connections
  smb/server: fix session counter on session removal
  smb/server: update session counter under sessions table lock
  smb/server: fix session leak in ksmbd_session_register()
  smb/server: warn if ksmbd_proc_create() fails
  ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size
  ksmbd: make RDMA encryption diagnostics conditional
  ksmbd: add SMB Direct RDMA encryption transform
  ksmbd: handle encrypted compressed requests
  ksmbd: decrypt requests from expired encrypted sessions
  ksmbd: disconnect on SMB3 decryption failure
  ksmbd: encrypt interim responses to encrypted requests
  ksmbd: scope session state changes to bound connections
  ksmbd: fix encrypted request lookup on bound channels
  ksmbd: add per-share SMB3 encryption enforcement
  ...

Pull kthread vfs updates from Christian Brauner:
 "This stops kernel threads from sharing filesystem state with
  userspace. This work is about 3 cycles old and has been in -next
  for about that time.

  When the kernel boots init_task creates PID 1 and then kthreadd. From
  that point every kthread and PID 1 share the same fs_struct. That is
  why pivot_root() has to rewrite the fs_struct of all kthreads. The
  rewriting exists so that kthreads can use init's filesystem state when
  they want to. It also means userspace can move the ground out from
  under the kernel.

  PID 1 now gets a completely separate fs_struct. All kthreads are
  anchored in a private SB_KERNMOUNT instance of nullfs that cannot be
  mounted on and cannot be used to follow other mounts. Userspace init
  can no longer affect kthread filesystem state and kthreads can no
  longer affect userspace fs state without explicit opting in to that.

  Path lookup from a kthread now fails by default. It makes it
  deliberately hard to offload security sensitive operations into init's
  filesystem state from a kthread.

  Places that legitimately need to look something up there opt in
  through the new scoped_with_init_fs() which temporarily overrides the
  caller's fs_struct with init's. usermodehelpers remain the only kernel
  tasks that genuinely share init's filesystem state, since they execute
  random binaries in the root filesystem (excellent...).

  The visible result is that /proc/2/root is a nullfs with an empty
  mountinfo while /proc/1/root is the real root"

* tag 'vfs-7.3-rc1.kthread' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (26 commits)
  initramfs_test: use test init/exit hooks to override init fs
  fs: stop rewriting paths for PF_EXITING | PF_DUMPCORE
  fs: stop rewriting kthread fs structs
  fs: start all kthreads in nullfs
  nullfs: make nullfs multi-instance
  devtmpfs: create private mount namespace
  fs: add umh argument to struct kernel_clone_args
  fs: stop sharing fs_struct between init_task and pid 1
  af_unix: use scoped_with_init_fs() for coredump socket lookup
  initramfs: use scoped_with_init_fs() for rootfs unpacking
  pnfs/blocklayout: use scoped_with_init_fs() for SCSI device lookup
  ksmbd: use scoped_with_init_fs() for VFS path operations
  ksmbd: use scoped_with_init_fs() for filesystem info path lookup
  ksmbd: use scoped_with_init_fs() for share path resolution
  fs: use scoped_with_init_fs() for kernel_read_file_from_path_initns()
  coredump: use scoped_with_init_fs() for coredump path resolution
  btrfs: use scoped_with_init_fs() for update_dev_time()
  scsi: target: use scoped_with_init_fs() for APTPL metadata
  scsi: target: use scoped_with_init_fs() for ALUA metadata
  crypto: ccp: use scoped_with_init_fs() for SEV file access
  ...

See the procedure below:

  smb2_sess_setup
    ksmbd_smb2_session_create
      __session_create
        hash_add(sessions_table, &sess->hlist, sess->id)
        ksmbd_counter_inc(KSMBD_COUNTER_SESSIONS)
  ksmbd_conn_handler_loop
    ksmbd_server_terminate_conn
      ksmbd_sessions_deregister
        hash_del(&sess->hlist)
        // do not decrement KSMBD_COUNTER_SESSIONS

KSMBD_COUNTER_SESSIONS tracks sessions published in sessions_table, but
session removal does not decrement it. The value therefore keeps growing
after sessions are expired, rejected during registration, or removed on
the last channel disconnect.

Fixes: b38f99c1217a ("ksmbd: add procfs interface for runtime monitoring and statistics")
Signed-off-by: Ze Tan <tanze@kylinos.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

KSMBD_COUNTER_SESSIONS tracks sessions published in sessions_table.
Increment it while holding sessions_table_lock so publishing a session and
updating the counter happen together.

Fixes: b38f99c1217a ("ksmbd: add procfs interface for runtime monitoring and statistics")
Signed-off-by: Ze Tan <tanze@kylinos.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

See the procedure below:

  smb2_sess_setup
    ksmbd_smb2_session_create
      __session_create
        atomic_set(&sess->refcnt, 2)
        hash_add(sessions_table, &sess->hlist, sess->id)
    ksmbd_session_register
      xa_store(&conn->sessions, sess->id, sess) // fail
    ksmbd_user_session_put
      atomic_dec(&sess->refcnt) // refcnt is 1, session is not freed

Remove the session from sessions_table and drop its table reference if
xa_store() fails.

Fixes: f5c779b7ddbd ("ksmbd: fix racy issue from session setup and logoff")
Signed-off-by: Ze Tan <tanze@kylinos.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

Print a warning if the sessions procfs entry cannot be created.

Signed-off-by: Ze Tan <tanze@kylinos.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

ksmbd_all_conn_set_status() treats every connection whose transient
binding flag is set as belonging to the target SessionId.  A logoff or
session replacement can consequently move an unrelated connection to
NEED_RECONNECT or NEED_SETUP.

Pass the target session itself and select connections using either the
connection-local session xarray or the session's permanent channel list.
Use the same association test while waiting for requests to drain.

Serialize session-wide status changes under request_lock and do not
overwrite EXITING or RELEASING. Protect the shutdown transition with the
same lock so a concurrent session update cannot revive a closing
connection.

Fixes: f5a544e3bab7 ("ksmbd: add support for SMB3 multichannel")
Fixes: abcc506a9a71 ("ksmbd: fix racy issue from smb2 close and logoff with multichannel")
Fixes: c444139cb747 ("ksmbd: rewrite stop_sessions() with restartable iteration")
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>