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Date: Mon, 25 Jul 2016 13:54:54 -0700 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Will Deacon <will.deacon@....com>, Russell King <linux@...linux.org.uk>, Steve Capper <steve.capper@....com>, Catalin Marinas <catalin.marinas@....com>, Russell King <rmk+kernel@....linux.org.uk> Subject: [PATCH 4.4 039/146] ARM: 8579/1: mm: Fix definition of pmd_mknotpresent 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Steve Capper <steve.capper@....com> commit 56530f5d2ddc9b9fade7ef8db9cb886e9dc689b5 upstream. 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. [catalin.marinas@....com: using L_PMD_SECT_VALID instead of PMD_TYPE_SECT] Fixes: 8d9625070073 ("ARM: mm: Transparent huge page support for LPAE systems.") Reported-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> Acked-by: Will Deacon <will.deacon@....com> Cc: Russell King <linux@...linux.org.uk> Signed-off-by: Steve Capper <steve.capper@....com> Signed-off-by: Catalin Marinas <catalin.marinas@....com> Signed-off-by: Russell King <rmk+kernel@....linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- arch/arm/include/asm/pgtable-3level.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/arch/arm/include/asm/pgtable-3level.h +++ b/arch/arm/include/asm/pgtable-3level.h @@ -258,10 +258,10 @@ 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) & ~L_PMD_SECT_VALID); } static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
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