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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: > Signed-off-by: Kefeng Wang > --- > 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(-) > > diff --git a/mm/migrate_device.c b/mm/migrate_device.c > index 052167f9ad54..6e711381f092 100644 > --- a/mm/migrate_device.c > +++ b/mm/migrate_device.c > @@ -411,7 +411,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > bool anon_exclusive; > pte_t swp_pte; > > - flush_cache_page(vma, addr, pte_pfn(pte)); > + if (pte_present(pte)) > + flush_cache_page(vma, addr, pte_pfn(pte)); > anon_exclusive = folio_test_anon(folio) && > PageAnonExclusive(page); > if (anon_exclusive) { > @@ -432,7 +433,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > migrate->cpages++; > > /* Set the dirty flag on the folio now the pte is gone. */ > - if (pte_dirty(pte)) > + if (pte_present(pte) && pte_dirty(pte)) > folio_mark_dirty(folio); > > /* Setup special migration page table entry */ > -- Makes sense, thanks! Reviewed-by: Balbir Singh