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> --- 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) { -- 2.39.1
