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From: Lance Yang <ioworker0@gmail.com>
Date: Fri, 24 May 2024 11:54:01 +0800
Message-ID: <CAK1f24kfV0wHVFTmp7YdWMRB8jzncHTiM91kTn9dBtgfnqwdYQ@mail.gmail.com>
Subject: Re: [PATCH] mm: arm64: Fix the out-of-bounds issue in contpte_clear_young_dirty_ptes
To: Barry Song <21cnbao@gmail.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org, 
	linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, 
	Barry Song <v-songbaohua@oppo.com>, Ryan Roberts <ryan.roberts@arm.com>, 
	David Hildenbrand <david@redhat.com>, Jeff Xie <xiehuan09@gmail.com>, 
	Kefeng Wang <wangkefeng.wang@huawei.com>, Michal Hocko <mhocko@suse.com>, 
	Minchan Kim <minchan@kernel.org>, Muchun Song <songmuchun@bytedance.com>, 
	Peter Xu <peterx@redhat.com>, Yang Shi <shy828301@gmail.com>, 
	Yin Fengwei <fengwei.yin@intel.com>, "Zach O'Keefe" <zokeefe@google.com>, 
	Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>
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Thanks a lot for reaching out, Barry!

On Fri, May 24, 2024 at 8:55=E2=80=AFAM Barry Song <21cnbao@gmail.com> wrot=
e:
>
> From: Barry Song <v-songbaohua@oppo.com>
>
> 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 h=
elper")
> Cc: Lance Yang <ioworker0@gmail.com>
> Cc: Barry Song <21cnbao@gmail.com>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Jeff Xie <xiehuan09@gmail.com>
> Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Muchun Song <songmuchun@bytedance.com>
> Cc: Peter Xu <peterx@redhat.com>
> Cc: Yang Shi <shy828301@gmail.com>
> Cc: Yin Fengwei <fengwei.yin@intel.com>
> Cc: Zach O'Keefe <zokeefe@google.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>

LGTM.

Acked-by: Lance Yang <ioworker0@gmail.com>

> Signed-off-by: Barry Song <v-songbaohua@oppo.com>
> ---
>  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_st=
ruct *vma,
>          * clearing access/dirty for the whole block.
>          */
>         unsigned long start =3D addr;
> -       unsigned long end =3D start + nr;
> +       unsigned long end =3D start + nr * PAGE_SIZE;
>
>         if (pte_cont(__ptep_get(ptep + nr - 1)))
>                 end =3D ALIGN(end, CONT_PTE_SIZE);
> @@ -386,7 +386,7 @@ void contpte_clear_young_dirty_ptes(struct vm_area_st=
ruct *vma,
>                 ptep =3D contpte_align_down(ptep);
>         }
>
> -       __clear_young_dirty_ptes(vma, start, ptep, end - start, flags);
> +       __clear_young_dirty_ptes(vma, start, ptep, (end - start) / PAGE_S=
IZE, flags);
>  }
>  EXPORT_SYMBOL_GPL(contpte_clear_young_dirty_ptes);
>
> --
> 2.34.1
>