2016-01-06 18:54 GMT+03:00 Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>:
> The original x86_64-only version of KASAN mapped its zero page
> read-only, but this got lost when the code was generalised and
> ported to arm64, since, at the time, the PAGE_KERNEL_RO define
> did not exist. It has been added to arm64 in the mean time, so
> let's use it.
>
Read-only wasn't lost. Just look at the next line:
zero_pte = pte_wrprotect(zero_pte);
PAGE_KERNEL_RO is not available on all architectures, thus it would be better
to not use it in generic code.
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
> mm/kasan/kasan_init.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/kasan/kasan_init.c b/mm/kasan/kasan_init.c
> index 3f9a41cf0ac6..8726a92604ad 100644
> --- a/mm/kasan/kasan_init.c
> +++ b/mm/kasan/kasan_init.c
> @@ -49,7 +49,7 @@ static void __init zero_pte_populate(pmd_t *pmd, unsigned long addr,
> pte_t *pte = pte_offset_kernel(pmd, addr);
> pte_t zero_pte;
>
> - zero_pte = pfn_pte(PFN_DOWN(__pa(kasan_zero_page)), PAGE_KERNEL);
> + zero_pte = pfn_pte(PFN_DOWN(__pa(kasan_zero_page)), PAGE_KERNEL_RO);
> zero_pte = pte_wrprotect(zero_pte);
>
> while (addr + PAGE_SIZE <= end) {
> --
> 2.5.0
>
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