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

[Liam R. Howlett]

* Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> [230814 15:15]:
> On Mon, 14 Aug 2023 16:54:01 +0200 Jann Horn <jannh@xxxxxxxxxx> 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);
> _
>