From 632ba61bd5ce649581691125a8adfbc581ffc164 Mon Sep 17 00:00:00 2001 From: Mike Rapoport Date: Thu, 22 Apr 2021 16:43:27 +1000 Subject: [PATCH] secretmem/gup: don't check if page is secretmem without reference The check in gup_pte_range() whether a page belongs to a secretmem mapping is performed before grabbing the page reference. To avoid potential race move the check after try_grab_compound_head(). Link: https://lkml.kernel.org/r/20210420150049.14031-2-rppt@kernel.org Signed-off-by: Mike Rapoport Reviewed-by: David Hildenbrand Signed-off-by: Andrew Morton Signed-off-by: Stephen Rothwell --- mm/gup.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/gup.c b/mm/gup.c index c3a17b189064..6515f82b0f32 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -2080,13 +2080,15 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, VM_BUG_ON(!pfn_valid(pte_pfn(pte))); page = pte_page(pte); - if (page_is_secretmem(page)) - goto pte_unmap; - head = try_grab_compound_head(page, 1, flags); if (!head) goto pte_unmap; + if (unlikely(page_is_secretmem(page))) { + put_compound_head(head, 1, flags); + goto pte_unmap; + } + if (unlikely(pte_val(pte) != pte_val(*ptep))) { put_compound_head(head, 1, flags); goto pte_unmap; -- 2.50.1