From e3a1f6cac1fe20e7ac01d96c914c25726723a64e Mon Sep 17 00:00:00 2001 From: David Vrabel Date: Thu, 19 Feb 2015 13:06:53 +0000 Subject: [PATCH] x86: pte_protnone() and pmd_protnone() must check entry is not present Since _PAGE_PROTNONE aliases _PAGE_GLOBAL it is only valid if _PAGE_PRESENT is clear. Make pte_protnone() and pmd_protnone() check for this. This fixes a 64-bit Xen PV guest regression introduced by 8a0516ed8b90 ("mm: convert p[te|md]_numa users to p[te|md]_protnone_numa"). Any userspace process would endlessly fault. In a 64-bit PV guest, userspace page table entries have _PAGE_GLOBAL set by the hypervisor. This meant that any fault on a present userspace entry (e.g., a write to a read-only mapping) would be misinterpreted as a NUMA hinting fault and the fault would not be correctly handled, resulting in the access endlessly faulting. Signed-off-by: David Vrabel Acked-by: Mel Gorman Signed-off-by: Linus Torvalds --- arch/x86/include/asm/pgtable.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 67fc3d2b0aab..a0c35bf6cb92 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -476,12 +476,14 @@ static inline int pmd_present(pmd_t pmd) */ static inline int pte_protnone(pte_t pte) { - return pte_flags(pte) & _PAGE_PROTNONE; + return (pte_flags(pte) & (_PAGE_PROTNONE | _PAGE_PRESENT)) + == _PAGE_PROTNONE; } static inline int pmd_protnone(pmd_t pmd) { - return pmd_flags(pmd) & _PAGE_PROTNONE; + return (pmd_flags(pmd) & (_PAGE_PROTNONE | _PAGE_PRESENT)) + == _PAGE_PROTNONE; } #endif /* CONFIG_NUMA_BALANCING */ -- GitLab