ksmbd: fix maximal access leak when object has no NT ACL

smb2_open()'s maximal-access handling sets maximal_access to the
FILE_MAXIMAL_ACCESS_LE request sentinel, then calls
smb_check_perm_dacl() to compute the real access mask from the
object's DACL.

smb_check_perm_dacl() returns success without touching *pdaccess when
the object has no stored NT ACL xattr (ksmbd_vfs_get_sd_xattr() fails,
taking an early goto err_out with rc still 0). This leaves
maximal_access holding the raw FILE_MAXIMAL_ACCESS_LE sentinel instead
of a real access mask.

Observed live: a freshly-created share root shows macOS's "no entry"
(prohibited-access) badge on connect, even though POSIX permissions
clearly allow access -- macOS requests maximal access via the MxAc
create context on every share-root open, not via DesiredAccess, so it
trusts the leaked sentinel verbatim instead of falling through to the
correct POSIX-based path.

Fall back to ksmbd_vfs_query_maximal_access() -- the same POSIX-based
computation already used for the DesiredAccess-requested-maximal-access
case below -- whenever the sentinel comes back unmodified.

Signed-off-by: Gael Blivet <gael.blivet@gmail.com>
Assisted-by: Claude:claude-sonnet-5
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

0 files changed, 0 insertions, 0 deletions