From mboxrd@z Thu Jan 1 00:00:00 1970 From: steve.capper@arm.com (Steve Capper) Date: Wed, 2 Mar 2016 01:03:00 +0000 Subject: [PATCH] arm: mm: Fix definition of pmd_mknotpresent Message-ID: <1456880580-22311-1-git-send-email-steve.capper@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Currently pmd_mknotpresent will use a zero entry to respresent an invalidated pmd. Unfortunately this definition clashes with pmd_none, thus it is possible for a race condition to occur if zap_pmd_range sees pmd_none whilst __split_huge_pmd_locked is running too with pmdp_invalidate just called. This patch fixes the race condition by modifying pmd_mknotpresent to create non-zero faulting entries (as is done in other architectures), removing the ambiguity with pmd_none. Fixes: 8d9625070073 ("ARM: mm: Transparent huge page support for LPAE systems.") Reported-by: Kirill A. Shutemov Signed-off-by: Steve Capper Acked-by: Will Deacon --- This patch addresses an issue discussed at: http://lkml.iu.edu/hypermail/linux/kernel/1602.3/01846.html --- arch/arm/include/asm/pgtable-3level.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h index dc46398..451b6e7 100644 --- a/arch/arm/include/asm/pgtable-3level.h +++ b/arch/arm/include/asm/pgtable-3level.h @@ -249,10 +249,10 @@ PMD_BIT_FUNC(mkyoung, |= PMD_SECT_AF); #define pfn_pmd(pfn,prot) (__pmd(((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))) #define mk_pmd(page,prot) pfn_pmd(page_to_pfn(page),prot) -/* represent a notpresent pmd by zero, this is used by pmdp_invalidate */ +/* represent a notpresent pmd by faulting entry, this is used by pmdp_invalidate */ static inline pmd_t pmd_mknotpresent(pmd_t pmd) { - return __pmd(0); + return __pmd(pmd_val(pmd) & ~PMD_TYPE_MASK); } static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot) -- 2.1.0