Re: [PATCH] mm: arm64: Fix the out-of-bounds issue in contpte_clear_young_dirty_ptes

[Lance Yang]

Thanks a lot for reaching out, Barry!

On Fri, May 24, 2024 at 8:55 AM Barry Song <21cnbao@xxxxxxxxx> wrote:
>
> From: Barry Song <v-songbaohua@xxxxxxxx>
>
> We are passing a huge nr to __clear_young_dirty_ptes() right
> now. While we should pass the number of pages, we are actually

Yes.

It's my mistake - sorry :(

> passing CONT_PTE_SIZE. This is causing lots of crashes of
> MADV_FREE, panic oops could vary everytime.
>
> Fixes: 89e86854fb0a ("mm/arm64: override clear_young_dirty_ptes() batch helper")
> Cc: Lance Yang <ioworker0@xxxxxxxxx>
> Cc: Barry Song <21cnbao@xxxxxxxxx>
> Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Cc: Jeff Xie <xiehuan09@xxxxxxxxx>
> Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> Cc: Peter Xu <peterx@xxxxxxxxxx>
> Cc: Yang Shi <shy828301@xxxxxxxxx>
> Cc: Yin Fengwei <fengwei.yin@xxxxxxxxx>
> Cc: Zach O'Keefe <zokeefe@xxxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>

LGTM.

Acked-by: Lance Yang <ioworker0@xxxxxxxxx>

> Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
> ---
>  arch/arm64/mm/contpte.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c
> index 9f9486de0004..a3edced29ac1 100644
> --- a/arch/arm64/mm/contpte.c
> +++ b/arch/arm64/mm/contpte.c
> @@ -376,7 +376,7 @@ void contpte_clear_young_dirty_ptes(struct vm_area_struct *vma,
>          * clearing access/dirty for the whole block.
>          */
>         unsigned long start = addr;
> -       unsigned long end = start + nr;
> +       unsigned long end = start + nr * PAGE_SIZE;
>
>         if (pte_cont(__ptep_get(ptep + nr - 1)))
>                 end = ALIGN(end, CONT_PTE_SIZE);
> @@ -386,7 +386,7 @@ void contpte_clear_young_dirty_ptes(struct vm_area_struct *vma,
>                 ptep = contpte_align_down(ptep);
>         }
>
> -       __clear_young_dirty_ptes(vma, start, ptep, end - start, flags);
> +       __clear_young_dirty_ptes(vma, start, ptep, (end - start) / PAGE_SIZE, flags);
>  }
>  EXPORT_SYMBOL_GPL(contpte_clear_young_dirty_ptes);
>
> --
> 2.34.1
>