On 13.02.2023 22:43, Vishal Moola (Oracle) wrote: > release_pte_pages() converts from a pfn to a folio by using pfn_folio(). > If the pte is not mapped, pfn_folio() will result in undefined behavior > which ends up causing a kernel panic[1]. > > Only call pfn_folio() once we have validated that the pte is both valid > and mapped to fix the issue. > > [1] https://lore.kernel.org/linux-mm/ff300770-afe9-908d-23ed-d23e0796e899@xxxxxxxxxxx/ > > Fixes: 9bdfeea46f49 ("mm/khugepaged: convert release_pte_pages() to use folios") > Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> > Debugged-by: Alexandre Ghiti <alex@xxxxxxxx> > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > Signed-off-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx> Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> > --- > mm/khugepaged.c | 14 ++++++++++---- > 1 file changed, 10 insertions(+), 4 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index b39ab219d5b7..bd54b957f69a 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -511,11 +511,17 @@ static void release_pte_pages(pte_t *pte, pte_t *_pte, > > while (--_pte >= pte) { > pte_t pteval = *_pte; > + unsigned long pfn; > > - folio = pfn_folio(pte_pfn(pteval)); > - if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)) && > - !folio_test_large(folio)) > - release_pte_folio(folio); > + if (pte_none(pteval)) > + continue; > + pfn = pte_pfn(pteval); > + if (is_zero_pfn(pfn)) > + continue; > + folio = pfn_folio(pfn); > + if (folio_test_large(folio)) > + continue; > + release_pte_folio(folio); > } > > list_for_each_entry_safe(folio, tmp, compound_pagelist, lru) { Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
