published September 25, 2026
In the Linux kernel, the following vulnerability has been resolved:
smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid
When the administrator mounts with forceuid or forcegid (uid=/gid=
mount options), they expect all files to appear owned by the specified
user/group. However, several code paths unconditionally called
sid_to_id() to overwrite cf_uid/cf_gid with server-provided values,
ignoring the administrator's explicit override:
- smb311_posix_info_to_fattr() (stat via POSIX extensions)
- cifs_posix_to_fattr() (readdir via POSIX extensions)
- parse_sec_desc() (CIFS ACL ownership mapping)
This allowed an untrusted server to dictate local file ownership even
when the mount was configured to force specific uid/gid values.
Fix all three call sites to check CIFS_MOUNT_OVERR_UID and
CIFS_MOUNT_OVERR_GID before calling sid_to_id(), following the
same pattern already used by cifs_unix_basic_to_fattr() for unix
extensions.