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

[Baolin Wang <baolin.wang@linux.alibaba.com>]

On 2024/5/24 08:54, Barry Song wrote:
> 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
> 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@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>
> Signed-off-by: Barry Song <v-songbaohua@oppo.com>

Good catch. Feel free to add:
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.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_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);
>