Commit 227ca9f6 authored by Huacai Chen's avatar Huacai Chen
Browse files

LoongArch: Disable KASAN if PGDIR_SIZE is too large for cpu_vabits 



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: default avatarJiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent a4106566

arch/loongarch/include/asm/kasan.h

+1 −1
Original line number Diff line number Diff line
@@ -51,7 +51,7 @@ 
/* KAsan shadow memory start right after vmalloc. */

#define KASAN_SHADOW_START		round_up(KFENCE_AREA_END, PGDIR_SIZE)

#define KASAN_SHADOW_SIZE		(XKVRANGE_VC_SHADOW_END - XKPRANGE_CC_KASAN_OFFSET)

#define KASAN_SHADOW_END		round_up(KASAN_SHADOW_START + KASAN_SHADOW_SIZE, PGDIR_SIZE)

#define KASAN_SHADOW_END		(round_up(KASAN_SHADOW_START + KASAN_SHADOW_SIZE, PGDIR_SIZE) - 1)



#define XKPRANGE_CC_SHADOW_OFFSET	(KASAN_SHADOW_START + XKPRANGE_CC_KASAN_OFFSET)

#define XKPRANGE_UC_SHADOW_OFFSET	(KASAN_SHADOW_START + XKPRANGE_UC_KASAN_OFFSET)

arch/loongarch/mm/kasan_init.c

+13 −2
Original line number Diff line number Diff line
@@ -238,7 +238,7 @@ static void __init kasan_map_populate(unsigned long start, unsigned long end, 
asmlinkage void __init kasan_early_init(void)

{

	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));

	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));

	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END + 1, PGDIR_SIZE));

}



static inline void kasan_set_pgd(pgd_t *pgdp, pgd_t pgdval)
@@ -253,7 +253,7 @@ static void __init clear_pgds(unsigned long start, unsigned long end) 
	 * swapper_pg_dir. pgd_clear() can't be used

	 * here because it's nop on 2,3-level pagetable setups

	 */

	for (; start < end; start += PGDIR_SIZE)

	for (; start < end; start = pgd_addr_end(start, end))

		kasan_set_pgd((pgd_t *)pgd_offset_k(start), __pgd(0));

}
@@ -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