Re: [PATCH v7 06/17] mm/nommu: fix the last places where vma is not locked before being attached

[Liam R. Howlett]

* Suren Baghdasaryan <surenb@xxxxxxxxxx> [241226 12:07]:
> nommu configuration has two places where vma gets attached to the vma tree
> without write-locking it. Add the missing locks to ensure vma is always
> locked before it's attached.

Does the delete side need to write lock as well?

> 
> Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> ---
>  mm/nommu.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 72c8c505836c..1754e84e5758 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -1189,6 +1189,7 @@ unsigned long do_mmap(struct file *file,
>  		goto error_just_free;
>  
>  	setup_vma_to_mm(vma, current->mm);
> +	vma_start_write(vma);
>  	current->mm->map_count++;
>  	/* add the VMA to the tree */
>  	vma_iter_store(&vmi, vma, true);
> @@ -1356,6 +1357,7 @@ static int split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
>  
>  	setup_vma_to_mm(vma, mm);
>  	setup_vma_to_mm(new, mm);
> +	vma_start_write(new);
>  	vma_iter_store(vmi, new, true);
>  	mm->map_count++;
>  	return 0;
> -- 
> 2.47.1.613.gc27f4b7a9f-goog
>