Magic number safeguard

Such protection mechanism, a specific sequence of actions that needs to be done before doing anything potentially dangerous should and can be implemented by the hardware, and is already done in e.g. some microcontrollers to protect flash/eprom from accidental writes.

It can't be done in software in the kernel. Or rather, it can, but is useless, because only functions that think they're going to do something dangerous do the checking, while in this case it's a regular cpu instruction that caused the corruption.