From 12eb3c2c1a4f6e7c30de2aa0a09cb1b9e19fa9c0 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Tue, 15 Jun 2021 18:23:16 -0700 Subject: mm/swap: fix pte_same_as_swp() not removing uffd-wp bit when compare commit 099dd6878b9b12d6bbfa6bf29ce0c8ddd38f6901 upstream. I found it by pure code review, that pte_same_as_swp() of unuse_vma() didn't take uffd-wp bit into account when comparing ptes. pte_same_as_swp() returning false negative could cause failure to swapoff swap ptes that was wr-protected by userfaultfd. Link: https://lkml.kernel.org/r/20210603180546.9083-1-peterx@redhat.com Fixes: f45ec5ff16a7 ("userfaultfd: wp: support swap and page migration") Signed-off-by: Peter Xu Acked-by: Hugh Dickins Cc: Andrea Arcangeli Cc: [5.7+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- include/linux/swapops.h | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) (limited to 'include') diff --git a/include/linux/swapops.h b/include/linux/swapops.h index d9b7c9132c2f..6430a94c6981 100644 --- a/include/linux/swapops.h +++ b/include/linux/swapops.h @@ -23,6 +23,16 @@ #define SWP_TYPE_SHIFT (BITS_PER_XA_VALUE - MAX_SWAPFILES_SHIFT) #define SWP_OFFSET_MASK ((1UL << SWP_TYPE_SHIFT) - 1) +/* Clear all flags but only keep swp_entry_t related information */ +static inline pte_t pte_swp_clear_flags(pte_t pte) +{ + if (pte_swp_soft_dirty(pte)) + pte = pte_swp_clear_soft_dirty(pte); + if (pte_swp_uffd_wp(pte)) + pte = pte_swp_clear_uffd_wp(pte); + return pte; +} + /* * Store a type+offset into a swp_entry_t in an arch-independent format */ @@ -66,10 +76,7 @@ static inline swp_entry_t pte_to_swp_entry(pte_t pte) { swp_entry_t arch_entry; - if (pte_swp_soft_dirty(pte)) - pte = pte_swp_clear_soft_dirty(pte); - if (pte_swp_uffd_wp(pte)) - pte = pte_swp_clear_uffd_wp(pte); + pte = pte_swp_clear_flags(pte); arch_entry = __pte_to_swp_entry(pte); return swp_entry(__swp_type(arch_entry), __swp_offset(arch_entry)); } -- cgit v1.2.3