On 10/11/2017 01:22 AM, Abbott Liu wrote:
> Because the kasan_zero_page(which is used as the shadow
> region for some memory that KASan doesn't need to track.) won't be writen
> after kasan_init, so change the mapping of kasan_zero_page into readonly.
>
> Cc: Andrey Ryabinin <a.ryabinin@xxxxxxxxxxx>
> ---
> arch/arm/mm/kasan_init.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/arch/arm/mm/kasan_init.c b/arch/arm/mm/kasan_init.c
> index 7cfdc39..c11826a 100644
> --- a/arch/arm/mm/kasan_init.c
> +++ b/arch/arm/mm/kasan_init.c
> @@ -200,6 +200,7 @@ void __init kasan_init(void)
> {
> struct memblock_region *reg;
> u64 orig_ttbr0;
> + int i;
Nit: unsigned int i.
>
> orig_ttbr0 = cpu_get_ttbr(0);
>
> @@ -243,6 +244,17 @@ void __init kasan_init(void)
> create_mapping((unsigned long)kasan_mem_to_shadow((void *)MODULES_VADDR),
> (unsigned long)kasan_mem_to_shadow((void *)(PKMAP_BASE+PMD_SIZE)),
> NUMA_NO_NODE);
> +
> + /*
> + * KAsan may reuse the contents of kasan_zero_pte directly, so we
> + * should make sure that it maps the zero page read-only.
> + */
> + for (i = 0; i < PTRS_PER_PTE; i++)
> + set_pte_at(&init_mm, KASAN_SHADOW_START + i*PAGE_SIZE,
> + &kasan_zero_pte[i], pfn_pte(
> + virt_to_pfn(kasan_zero_page),
> + __pgprot(_L_PTE_DEFAULT | L_PTE_DIRTY | L_PTE_XN | L_PTE_RDONLY)));
> + memset(kasan_zero_page, 0, PAGE_SIZE);
> cpu_set_ttbr0(orig_ttbr0);
> flush_cache_all();
> local_flush_bp_all();
>
--
Florian
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