Re: [PATCH v3 5/7] mm/memfd_luo: fix physical address conversion in put_folios cleanup

[Pasha Tatashin <pasha.tatashin@soleen.com>]

On Thu, Mar 26, 2026 at 4:48 AM Chenghao Duan <duanchenghao@kylinos.cn> wrote:
>
> In memfd_luo_retrieve_folios()'s put_folios cleanup path:
>
> 1. kho_restore_folio() expects a phys_addr_t (physical address) but
>    receives a raw PFN (pfolio->pfn). This causes kho_restore_page() to
>    check the wrong physical address (pfn << PAGE_SHIFT instead of the
>    actual physical address).
>
> 2. This loop lacks the !pfolio->pfn check that exists in the main
>    retrieval loop and memfd_luo_discard_folios(), which could
>    incorrectly process sparse file holes where pfn=0.
>
> Fix by converting PFN to physical address with PFN_PHYS() and adding
> the !pfolio->pfn check, matching the pattern used elsewhere in this file.
>
> This issue was identified by the AI review.
> https://sashiko.dev/#/patchset/20260323110747.193569-1-duanchenghao@kylinos.cn
>
> Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
> ---
>  mm/memfd_luo.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memfd_luo.c b/mm/memfd_luo.c
> index 76edf9a3f5b5..b4cea3670689 100644
> --- a/mm/memfd_luo.c
> +++ b/mm/memfd_luo.c
> @@ -469,8 +469,13 @@ static int memfd_luo_retrieve_folios(struct file *file,
>          */
>         for (long j = i + 1; j < nr_folios; j++) {
>                 const struct memfd_luo_folio_ser *pfolio = &folios_ser[j];
> +               phys_addr_t phys;
> +
> +               if (!pfolio->pfn)
> +                       continue;
>
> -               folio = kho_restore_folio(pfolio->pfn);
> +               phys = PFN_PHYS(pfolio->pfn);
> +               folio = kho_restore_folio(phys);

Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>

Thanks,
Pasha

>                 if (folio)
>                         folio_put(folio);
>         }
> --
> 2.25.1
>