The prctl call is a general interface for performing operations on a process. It only supports a single operation that sets or clears the signal that the calling process will receive when its parent dies. The existing Flask controls for signals ensure that the delivery of the signal is controlled. However, it would be useful to check the appropriate signal permission when this call is used so that the calling process will be aware of any permission failure.
The rt_sigqueueinfo call is a variant of kill for real-time signals. This call is already controlled through the existing Flask signal permissions.
The getpid and getppid calls may be used to obtain the process identifier of the calling process and its parent, respectively. The getpid call does not require any controls, since it only reveals private state of the calling process. The getppid call would only need to be controlled if it would be useful to conceal the PID of the parent, but such a need is not evident.