Per-process shared keyring
The process keyring is a keyring used to anchor keys on behalf of a process. It is only created when a process requests it.
A special serial number value, KEY_SPEC_PROCESS_KEYRING, is defined that can be used in lieu of the calling process's process keyring's actual serial number.
From the keyctl utility, '@p' can be used instead of a numeric key ID in much the same way, but as keyctl is a program run after forking, this is of no utility.
A process's process keyring is inherited across clone() with CLONE_THREAD and is cleared by execve(). The process keyring will be destroyed when the last thread that refers to it exits.
If a process doesn't have a process keyring when it is accessed, then the process keyring will be created if the keyring is to be modified, otherwise error ENOKEY will be issued.