If PGDIR_SIZE is too large for cpu_vabits, KASAN_SHADOW_END will overflow UINTPTR_MAX because KASAN_SHADOW_START/KASAN_SHADOW_END are aligned up by PGDIR_SIZE. And then the overflowed KASAN_SHADOW_END looks like a user space address. For example, PGDIR_SIZE of CONFIG_4KB_4LEVEL is 2^39, which is too large for Loongson-2K series whose cpu_vabits = 39. Since CONFIG_4KB_4LEVEL is completely legal for CPUs with cpu_vabits <= 39, we just disable KASAN via early return in kasan_init(). Otherwise we get a boot failure. Moreover, we change KASAN_SHADOW_END from the first address after KASAN shadow area to the last address in KASAN shadow area, in order to avoid the end address exactly overflow to 0 (which is a legal case). We don't need to worry about alignment because pgd_addr_end() can handle it. Cc: stable@vger.kernel.org Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>