macOS kernel return 13 (KERN_NAME_EXISTS): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: The requested Mach port name already denotes a right in the task's namespace.

Could be also:
Constant	Type	OS
ERROR_INVALID_DATA	Win32 error	Windows
ippStsLSFLow	Intel Ipp Status	Any
EACCES	errno	Any
MUTEX_LEVEL_NUMBER_VIOLATION	BugCheck Code	Windows

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KERN_NOT_IN_SET	KERN_ABORTED

KERN_NAME_EXISTS

KERN_NAME_EXISTS concerns a task-local Mach port namespace. The requested name already denotes a port right in that task, so Mach cannot use the same name for a separate right in the way the operation requested.

This is easy to misread if a log shows only the numeric port name. Mach port names are indexes in a task's namespace, not systemwide identifiers. The same numeric value can have a different meaning in another task, while one task cannot simultaneously use a name for two unrelated rights.

Useful checks

Find out whether the existing name denotes the right the code intended to install.
Review name allocation, renaming, and import paths for collisions.
Keep the port-right type with the name in diagnostics; a number alone is insufficient.
When importing rights across IPC, avoid assuming the sender's numeric name is reusable in the receiver's namespace.

The condition is not necessarily an access-denied failure. It says the local namespace already has an entry at that name. The correct outcome depends on whether that existing entry is expected, stale, or evidence of a resource-lifecycle bug.

References

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