Re: [PATCH] mm/hugetlb: fix null ptr defer in hugetlb_vma_lock_write

Rik van Riel
2023-11-03T00:57:23Z

On Thu, 2023-11-02 at 20:58 +0800, Edward Adam Davis wrote:
>
> +++ b/include/linux/hugetlb.h
>
> +#define HPAGE_RESV_OWNER    (1UL << 0)
>  static inline bool __vma_private_lock(struct vm_area_struct *vma)
>  {
> -       return (!(vma->vm_flags & VM_MAYSHARE)) && vma-
> >vm_private_data;
> +       return (!(vma->vm_flags & VM_MAYSHARE)) && vma-
> >vm_private_data &&
> +               is_vma_resv_set(vma, HPAGE_RESV_OWNER);
>  }
>
>  /*
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 1301ba7b2c9a..97ea782dfba6 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1033,7 +1033,6 @@ __weak unsigned long vma_mmu_pagesize(struct
> vm_area_struct *vma)
>   * bits of the reservation map pointer, which are always clear due
> to
>   * alignment.
>   */
> -#define HPAGE_RESV_OWNER    (1UL << 0)
>  #define HPAGE_RESV_UNMAPPED (1UL << 1)
>  #define HPAGE_RESV_MASK (HPAGE_RESV_OWNER | HPAGE_RESV_UNMAPPED)
>

Moving just that one define is less than ideal, and the
kernel test robot seems unhappy, too.

It may be cleaner to just move __vma_private_lock into
hugetlb.c, where it has all the dependencies it needs.

It isn't being called from anywhere else, anyway.

Hopefully that will keep the kernel test robot happy, too :)

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