linux-kernel - Re: [PATCH] mm/hugetlb: fix null ptr defer in hugetlb_vma_lock

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Message-ID: <32cb089b2afec5dc3bb96234753cca4b22cb9ccd.camel@surriel.com>
Date:   Thu, 02 Nov 2023 20:56:47 -0400
From:   Rik van Riel <riel@...riel.com>
To:     Edward Adam Davis <eadavis@...com>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, llvm@...ts.linux.dev, mike.kravetz@...cle.com,
        muchun.song@...ux.dev, nathan@...nel.org, ndesaulniers@...gle.com,
        syzbot+6ada951e7c0f7bc8a71e@...kaller.appspotmail.com,
        syzkaller-bugs@...glegroups.com, trix@...hat.com
Subject: Re: [PATCH] mm/hugetlb: fix null ptr defer in hugetlb_vma_lock_write

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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