On Fri, May 31, 2024 at 9:33 AM Liam R. Howlett <[email protected]> wrote:
>
> The vma iterator may be left pointing to the newly created vma. This
> happens when inserting the new vma at the end of the old vma
> (!new_below).
>
> The incorrect position in the vma iterator is not exposed currently
> since the vma iterator is repositioned in the munmap path and is not
> reused in any of the other paths.
>
> This has limited impact in the current code, but is required for future
> changes.
>
> Fixes: b2b3b886738f ("mm: don't use __vma_adjust() in __split_vma()")
> Signed-off-by: Liam R. Howlett <[email protected]>
> ---
> mm/mmap.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 83b4682ec85c..31d464e6a656 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2442,6 +2442,9 @@ static int __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
> /* Success. */
> if (new_below)
> vma_next(vmi);
> + else
> + vma_prev(vmi);
> +
IIUC the goal is to always point vmi to the old (original) vma? If so,
then change LGTM.
Reviewed-by: Suren Baghdasaryan <[email protected]>
> return 0;
>
> out_free_mpol:
> --
> 2.43.0
>
* Suren Baghdasaryan <[email protected]> [240605 20:51]:
> On Fri, May 31, 2024 at 9:33 AM Liam R. Howlett <[email protected]> wrote:
> >
> > The vma iterator may be left pointing to the newly created vma. This
> > happens when inserting the new vma at the end of the old vma
> > (!new_below).
> >
> > The incorrect position in the vma iterator is not exposed currently
> > since the vma iterator is repositioned in the munmap path and is not
> > reused in any of the other paths.
> >
> > This has limited impact in the current code, but is required for future
> > changes.
> >
> > Fixes: b2b3b886738f ("mm: don't use __vma_adjust() in __split_vma()")
> > Signed-off-by: Liam R. Howlett <[email protected]>
> > ---
> > mm/mmap.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index 83b4682ec85c..31d464e6a656 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -2442,6 +2442,9 @@ static int __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
> > /* Success. */
> > if (new_below)
> > vma_next(vmi);
> > + else
> > + vma_prev(vmi);
> > +
>
> IIUC the goal is to always point vmi to the old (original) vma? If so,
> then change LGTM.
Yes, we need the iterator to keep pointing to the original VMAs, I think
this makes sense. I will update the function comment in the next
revision to state as much.
>
> Reviewed-by: Suren Baghdasaryan <[email protected]>
>
> > return 0;
> >
> > out_free_mpol:
> > --
> > 2.43.0
> >