Enable init_on_free in GRUB kernel parameters

Description

The init_on_free=1 kernel parameter must be set so the kernel zeroes memory pages when they are freed. This clears freed memory to detect and prevent use-after-free attacks.

Rationale

Zeroing memory at free time removes stale sensitive data from freed pages and causes use-after-free vulnerabilities to read zeroed memory instead of attacker-controlled data, making kernel memory-corruption bugs harder to exploit.

Framework references

Live verification