Commit 56530f5d authored Jun 07, 2016 by Steve Capper Committed by Russell King Jun 09, 2016

ARM: 8579/1: mm: Fix definition of pmd_mknotpresent



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@arm.com: using L_PMD_SECT_VALID instead of PMD_TYPE_SECT]

Fixes: 8d962507 ("ARM: mm: Transparent huge page support for LPAE systems.")
Cc: <stable@vger.kernel.org> # 3.11+
Reported-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Signed-off-by: Steve Capper <steve.capper@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

parent 62453188

arch/arm/include/asm/pgtable-3level.h

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -250,10 +250,10 @@ PMD_BIT_FUNC(mkyoung, \|= PMD_SECT_AF);
	#define pfn_pmd(pfn,prot) (__pmd(((phys_addr_t)(pfn) << PAGE_SHIFT) \| pgprot_val(prot)))		#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)		#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)		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)		static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)