Le 01/09/2022 à 19:34, Suren Baghdasaryan a écrit :
> vma_adjust modifies a VMA and possibly its neighbors. Mark them as locked
> before making the modifications.
>
> Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> ---
> mm/mmap.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index f89c9b058105..ed58cf0689b2 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -710,6 +710,10 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
> long adjust_next = 0;
> int remove_next = 0;
>
> + vma_mark_locked(vma);
> + if (next)
> + vma_mark_locked(next);
> +
I was wondering if the VMAs insert and expand should be locked too.
For expand, I can't see any valid reason, but for insert, I'm puzzled.
I would think that it is better to lock the VMA to be inserted but I can't
really justify that.
It may be nice to detail why this is not need to lock insert and expand here.
> if (next && !insert) {
> struct vm_area_struct *exporter = NULL, *importer = NULL;
>
> @@ -754,8 +758,11 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
> * If next doesn't have anon_vma, import from vma after
> * next, if the vma overlaps with it.
> */
> - if (remove_next == 2 && !next->anon_vma)
> + if (remove_next == 2 && !next->anon_vma) {
> exporter = next->vm_next;
> + if (exporter)
> + vma_mark_locked(exporter);
> + }
>
> } else if (end > next->vm_start) {
> /*
> @@ -931,6 +938,8 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
> * "vma->vm_next" gap must be updated.
> */
> next = vma->vm_next;
> + if (next)
> + vma_mark_locked(next);
> } else {
> /*
> * For the scope of the comment "next" and
