Legacy Applications and the Privilege Model

To accommodate legacy applications, the implementation of privileges works with both the superuser and the privilege models. The kernel automatically tracks the PRIV_AWARE flag, which indicates that a program has been designed to work with privileges. Consider a child process that is not aware of privileges. Any privileges that were inherited from the parent process are available in the child's permitted and effective sets. If the child process sets a UID to 0, the child process might not have full superuser capabilities. The process's effective and permitted sets are restricted to those privileges in the child's limit set. Thus, the limit set of a privilege-aware process restricts the root privileges of child processes that are not aware of privileges.