[PATCH] LoongArch: Disable KASAN if PGDIR_SIZE is too large for cpu_vabits
From: Huacai Chen
Date: Wed Oct 30 2024 - 04:11:38 EST
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.
Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
---
arch/loongarch/mm/kasan_init.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/arch/loongarch/mm/kasan_init.c b/arch/loongarch/mm/kasan_init.c
index 4a0d1880dd71..6bdcc8751d4e 100644
--- a/arch/loongarch/mm/kasan_init.c
+++ b/arch/loongarch/mm/kasan_init.c
@@ -262,6 +262,17 @@ void __init kasan_init(void)
u64 i;
phys_addr_t pa_start, pa_end;
+ /*
+ * If PGDIR_SIZE is too large for cpu_vabits, KASAN_SHADOW_END will
+ * overflow UINTPTR_MAX and then 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.
+ */
+ if (KASAN_SHADOW_END < vm_map_base) {
+ pr_warn("PGDIR_SIZE too large for cpu_vabits, KernelAddressSanitizer disabled.\n");
+ return;
+ }
+
/*
* PGD was populated as invalid_pmd_table or invalid_pud_table
* in pagetable_init() which depends on how many levels of page
--
2.43.5