> There are tons of complicated ways to fix this. But the easiest way is > just to say that you need to keep PKRU set so that the signal frame can > be written at any time. Just for completeness sake, the signal frame was actually written successfully since I moved the stack pointer to pkey-1 associated memory before any exceptions, details in unix.stackexchange I <https://unix.stackexchange.com/questions/755160/memory-protection-keys-exception-handler-crashes-if-pkey0-is-write-disabled> posted in the beginning. And it’s probably that the kernel wants to write something else into pkey-0 associated memory. I understand that there is no easy solution, so my idea of isolating a user from corrupting pkey-0 memory is probably moot. Thanks Dave, that helped me a lot to understand the problem