[PATCH v1 1/1] riscv: mm: add missing memcpy in kasan_init

[Atish Patra]

On Sun, Oct 9, 2022 at 1:31 AM <panqinglin2020 at iscas.ac.cn> wrote:
>
> From: Qinglin Pan <panqinglin2020 at iscas.ac.cn>
>
> Hi Atish,
>
> It seems that the panic is due to the missing memcpy during kasan_init.
> Could you please check whether this patch is helpful?
>
> When doing kasan_populate, the new allocated base_pud/base_p4d should
> contain kasan_early_shadow_{pud, p4d}'s content. Add the missing memcpy
> to avoid page fault when read/write kasan shadow region.
>
> Tested on:
>  - qemu with sv57 and CONFIG_KASAN on.
>  - qemu with sv48 and CONFIG_KASAN on.
>
> Signed-off-by: Qinglin Pan <panqinglin2020 at iscas.ac.cn>
> ---
>  arch/riscv/mm/kasan_init.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/mm/kasan_init.c b/arch/riscv/mm/kasan_init.c
> index a22e418dbd82..e1226709490f 100644
> --- a/arch/riscv/mm/kasan_init.c
> +++ b/arch/riscv/mm/kasan_init.c
> @@ -113,6 +113,8 @@ static void __init kasan_populate_pud(pgd_t *pgd,
>                 base_pud = pt_ops.get_pud_virt(pfn_to_phys(_pgd_pfn(*pgd)));
>         } else if (pgd_none(*pgd)) {
>                 base_pud = memblock_alloc(PTRS_PER_PUD * sizeof(pud_t), PAGE_SIZE);
> +               memcpy(base_pud, (void *)kasan_early_shadow_pud,
> +                       sizeof(pud_t) * PTRS_PER_PUD);
>         } else {
>                 base_pud = (pud_t *)pgd_page_vaddr(*pgd);
>                 if (base_pud == lm_alias(kasan_early_shadow_pud)) {
> @@ -173,8 +175,11 @@ static void __init kasan_populate_p4d(pgd_t *pgd,
>                 base_p4d = pt_ops.get_p4d_virt(pfn_to_phys(_pgd_pfn(*pgd)));
>         } else {
>                 base_p4d = (p4d_t *)pgd_page_vaddr(*pgd);
> -               if (base_p4d == lm_alias(kasan_early_shadow_p4d))
> +               if (base_p4d == lm_alias(kasan_early_shadow_p4d)) {
>                         base_p4d = memblock_alloc(PTRS_PER_PUD * sizeof(p4d_t), PAGE_SIZE);
> +                       memcpy(base_p4d, (void *)kasan_early_shadow_p4d,
> +                               sizeof(p4d_t) * PTRS_PER_P4D);
> +               }
>         }
>
>         p4dp = base_p4d + p4d_index(vaddr);
> --
> 2.35.1
>

Yes. This patch fixes the boot issue for me with Kasan enabled on v6.0.

Tested-by: Atish Patra <atishp at rivosinc.com>

Thanks for the patch. Few nit comments:

You can drop the message addressed to me in the commit text.
Usually, that should be after the last sign off between two  "---"

As conor suggested, there should be a Fixes tag[1] in the commit text.

[1] https://www.kernel.org/doc/html/v4.10/process/submitting-patches.html#:~:text=A%20Fixes%3A%20tag%20indicates%20that,versions%20should%20receive%20your%20fix.
-- 
Regards,
Atish