From 722c05f2192070bac0208b2c16ce13929b32d92f Mon Sep 17 00:00:00 2001 From: Avi Kivity Date: Sun, 13 Jul 2008 11:33:54 +0300 Subject: [PATCH] KVM: MMU: Fix potential race setting upper shadow ptes on nonpae hosts The direct mapped shadow code (used for real mode and two dimensional paging) sets upper-level ptes using direct assignment rather than calling set_shadow_pte(). A nonpae host will split this into two writes, which opens up a race if another vcpu accesses the same memory area. Fix by calling set_shadow_pte() instead of assigning directly. Noticed by Izik Eidus. Signed-off-by: Avi Kivity --- arch/x86/kvm/mmu.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 7f57da663826..b0e4ddca6c18 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -1189,9 +1189,10 @@ static int __direct_map(struct kvm_vcpu *vcpu, gpa_t v, int write, return -ENOMEM; } - table[index] = __pa(new_table->spt) - | PT_PRESENT_MASK | PT_WRITABLE_MASK - | shadow_user_mask | shadow_x_mask; + set_shadow_pte(&table[index], + __pa(new_table->spt) + | PT_PRESENT_MASK | PT_WRITABLE_MASK + | shadow_user_mask | shadow_x_mask); } table_addr = table[index] & PT64_BASE_ADDR_MASK; } -- 2.20.1