Permissions are implemented as in Windows NTFS model, suggested reading:
The last reference is included:
Because of the fact that users have can have many different rights settings and objects can have many different permission settings, it is possible that conflicting permission settings might apply to a particular object and access method.
When this occurs, the system must engage in a process of resolving the various permissions to determine which ones should govern the access.
Here are some rules for resolving permissions conflicts:
Although Deny permissions generally take precedence over allow permissions, this is not always the case. An explicit "allow" permission can take precedence over an inherited "deny" permission.
The hierarchy of precedence for the permissions can be summarized as follows, with the higher precedence permissions listed at the top of the list:
Also true: File permissions override folder permissions, unless the Full Control permission has been granted to the folder.