Re: [PATCH v2] mm: migrate_device: fix pte_pfn/pte_dirty called on non-present PTE

["Zi Yan" <ziy@nvidia.com>]

On Tue Jul 7, 2026 at 8:39 PM EDT, Kefeng Wang wrote:
> pte_pfn() and pte_dirty() have undefined behaviour when called on a
> non-present PTE. In migrate_vma_collect_pmd(), these functions may be
> invoked on non-present entries (e.g., device-private entries), leading
> to potential crashes from pte_pfn() or incorrect dirty folio accounting
> from pte_dirty(). Fix both by guarding with pte_present() checks.
>
> Fixes: fd35ca3d12cc ("mm/migrate_device.c: copy pte dirty bit to page")
> Fixes: 6c287605fd56 ("mm: remember exclusively mapped anonymous pages with PG_anon_exclusive")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
> v2:
> - correct changelog and Fixes tags, suggested by David.
> - cc stable, suggested by Andrew.
>
>  mm/migrate_device.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
Acked-by: Zi Yan <ziy@nvidia.com>

-- 
Best Regards,
Yan, Zi