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

Liam R. Howlett
2025-01-07T17:51:55Z

* Suren Baghdasaryan <surenb@google.com> [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@google.com>
> ---
> 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
>