ksmbd: validate AppInstanceId takeover target

AppInstanceId lookup currently selects the first open with the matching
identifier. CREATE for an unrelated share or path can therefore
force-close another session's open before authorization of the new
target. Matching only the base path also conflates alternate data streams
with the unnamed stream.

MS-SMB2 requires the old open to match the share and path, belong to a
different ClientGuid, and be closed only when the requester has
GENERIC_READ access. Search all opens with the ID and match share,
resolved path, stream, and the current connection's client GUID. Retain a
share configuration reference in ksmbd_file and reuse its name instead of
allocating a name for every open. This keeps matching safe during tree
connection teardown and preserves name-based matching across configuration
updates.

Refresh the share reference on durable reconnect and restore the old
reference if reopening fails. Serialize connection and share comparisons
with durable disconnect/reconnect, and recheck the target before closing
it. Keep the original ClientGuid for durable replay and lease checks.

Check AppInstanceVersion before querying access, even when GENERIC_READ
is absent, and before disconnected delete-on-close cleanup. Rejected
CREATE must leave other durable opens untouched. Calculate maximal access
on the matched open's referenced path so a rename cannot substitute another
file's authorization. Require read access with the effective VFS
credentials as well as the NT DACL before takeover. Access denial only
skips takeover and leaves CREATE to its normal access checks. Restore
filesystem credentials before returning a takeover error.

Handle takeover before checking FILE_CREATE collisions, and re-resolve
the path after closing the old open. This lets delete-on-close remove the
old file before a new one is created. Include SYNCHRONIZE in the baseline
maximal-access mask so read-only files report GENERIC_READ correctly.

Fixes: 16c30649709d ("ksmbd: handle durable v2 app instance id")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Sung Byeongchan <tjdqudcks0424@naver.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

0 files changed, 0 insertions, 0 deletions