From 7566f4e19a27ec501a9843e4697dc99c8a2b5bea Mon Sep 17 00:00:00 2001 From: Christoffer Dall Date: Wed, 1 Jul 2015 14:08:31 +0200 Subject: [PATCH] arm64: Don't report clear pmds and puds as huge commit fd28f5d439fca77348c129d5b73043a56f8a0296 upstream. The current pmd_huge() and pud_huge() functions simply check if the table bit is not set and reports the entries as huge in that case. This is counter-intuitive as a clear pmd/pud cannot also be a huge pmd/pud, and it is inconsistent with at least arm and x86. To prevent others from making the same mistake as me in looking at code that calls these functions and to fix an issue with KVM on arm64 that causes memory corruption due to incorrect page reference counting resulting from this mistake, let's change the behavior. Signed-off-by: Christoffer Dall Reviewed-by: Steve Capper Acked-by: Marc Zyngier Fixes: 084bd29810a5 ("ARM64: mm: HugeTLB support.") Signed-off-by: Catalin Marinas Signed-off-by: Luis Henriques --- arch/arm64/mm/hugetlbpage.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c index 023747bf4dd7..e3a24b75e53c 100644 --- a/arch/arm64/mm/hugetlbpage.c +++ b/arch/arm64/mm/hugetlbpage.c @@ -46,13 +46,13 @@ struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address, int pmd_huge(pmd_t pmd) { - return !(pmd_val(pmd) & PMD_TABLE_BIT); + return pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT); } int pud_huge(pud_t pud) { #ifndef __PAGETABLE_PMD_FOLDED - return !(pud_val(pud) & PUD_TABLE_BIT); + return pud_val(pud) && !(pud_val(pud) & PUD_TABLE_BIT); #else return 0; #endif