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LoongArch: Disable KASAN if PGDIR_SIZE is too large for cpu_vabits

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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>
This commit is contained in:
Huacai Chen 2024-11-12 16:35:39 +08:00
parent a410656643
commit 227ca9f6f6
2 changed files with 14 additions and 3 deletions
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2
arch/loongarch/include/asm/kasan.h
View File

@ -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)

15
arch/loongarch/mm/kasan_init.c
View File

@ -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