linux-kernel - Re: [PATCH v4 5/6] mm: always lock new vma before inserting into vma tree

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Date:   Mon, 14 Aug 2023 22:02:15 +0200
From:   Jann Horn <jannh@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Suren Baghdasaryan <surenb@...gle.com>,
        torvalds@...ux-foundation.org, willy@...radead.org,
        liam.howlett@...cle.com, david@...hat.com, peterx@...hat.com,
        ldufour@...ux.ibm.com, vbabka@...e.cz, michel@...pinasse.org,
        jglisse@...gle.com, mhocko@...e.com, hannes@...xchg.org,
        dave@...olabs.net, hughd@...gle.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, kernel-team@...roid.com
Subject: Re: [PATCH v4 5/6] mm: always lock new vma before inserting into vma tree

On Mon, Aug 14, 2023 at 9:15 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
> On Mon, 14 Aug 2023 16:54:01 +0200 Jann Horn <jannh@...gle.com> wrote:
>
> > > @@ -403,6 +403,8 @@ static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma)
> > >
> > >   vma_iter_store(&vmi, vma);
> > >
> > > + vma_start_write(vma);
> > > +
> > >   if (vma->vm_file) {
> > >  mapping = vma->vm_file->f_mapping;
> > >  i_mmap_lock_write(mapping);
> >
> > The "vma_start_write()" has to be ordered before the
> > "vma_iter_store(&vmi, vma)".
>
> Thanks.  This?
>
>
> --- a/mm/mmap.c~mm-always-lock-new-vma-before-inserting-into-vma-tree-fix
> +++ a/mm/mmap.c
> @@ -401,10 +401,10 @@ static int vma_link(struct mm_struct *mm
>         if (vma_iter_prealloc(&vmi, vma))
>                 return -ENOMEM;
>
> -       vma_iter_store(&vmi, vma);
> -
>         vma_start_write(vma);
>
> +       vma_iter_store(&vmi, vma);
> +
>         if (vma->vm_file) {
>                 mapping = vma->vm_file->f_mapping;
>                 i_mmap_lock_write(mapping);

Yes, thanks, that looks good.