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 15:19:22 -0400
From:   "Liam R. Howlett" <Liam.Howlett@...cle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Jann Horn <jannh@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        torvalds@...ux-foundation.org, willy@...radead.org,
        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

* Andrew Morton <akpm@...ux-foundation.org> [230814 15:15]:
> 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?

Yes, this looks good.

> 
> 
> --- 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);
> _
>