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KERN_PROTECTION_FAILURE
KERN_PROTECTION_FAILURE means the address is valid in the target task, but the requested operation conflicts with the mapping's access protections. In other words, this is a protection problem, not evidence that the address range is absent.
This result commonly matters around Mach virtual-memory reads, writes, copies, or remapping. A process can share a range while keeping it read-only, and Mach uses protected sharing as part of copy-on-write behavior. A write into such a range can therefore fail even though a read or a region query succeeds.
How to diagnose it
- Identify the precise operation: read, write, execute, copy, or a mapping change.
- Inspect the target range's current protection and whether the operation spans more than one region.
- Do not treat it as a request to bypass macOS protection. The correct fix is normally to use an allowed operation or arrange the mapping with the needed rights.
- When inspecting another task, distinguish a task-port entitlement or authorization issue from the protection of the specific VM region.
Apple's Mach documentation describes virtual-memory ranges as mappings backed by memory objects. Their permissions are part of the mapping state, so a valid address alone is not sufficient for every kind of access.
References
- XNU: kern_return.h
- Apple Kernel Programming Guide: Mach overview
- GNU Mach Reference Manual: Virtual Memory Interface
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