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[184.147.118.108]) by smtp.gmail.com with ESMTPSA id d2sm2344846qkn.95.2021.06.03.11.05.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Jun 2021 11:05:47 -0700 (PDT) From: Peter Xu To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: peterx@redhat.com, Andrew Morton , Hugh Dickins , Andrea Arcangeli Subject: [PATCH] mm/swap: Fix pte_same_as_swp() not removing uffd-wp bit when compare Date: Thu, 3 Jun 2021 14:05:46 -0400 Message-Id: <20210603180546.9083-1-peterx@redhat.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Cc: Hugh Dickins Cc: Andrea Arcangeli Cc: Andrew Morton Signed-off-by: Peter Xu --- include/linux/swapops.h | 15 +++++++++++---- mm/swapfile.c | 2 +- 2 files changed, 12 insertions(+), 5 deletions(-) diff --git a/include/linux/swapops.h b/include/linux/swapops.h index af3d2661e41e..d356ab4047f7 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)); } diff --git a/mm/swapfile.c b/mm/swapfile.c index 6212bc033602..1e07d1c776f2 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1887,7 +1887,7 @@ unsigned int count_swap_pages(int type, int free) static inline int pte_same_as_swp(pte_t pte, pte_t swp_pte) { - return pte_same(pte_swp_clear_soft_dirty(pte), swp_pte); + return pte_same(pte_swp_clear_flags(pte), swp_pte); } /* -- 2.31.1