From ab442dfc820b6ebdbb1c135e6fad66130d44e5a8 Mon Sep 17 00:00:00 2001 From: Andrew Honig Date: Wed, 10 Jan 2018 10:12:03 -0800 Subject: [PATCH 03/33] KVM: x86: Add memory barrier on vmcs field lookup commit 75f139aaf896d6fdeec2e468ddfa4b2fe469bf40 upstream. This adds a memory barrier when performing a lookup into the vmcs_field_to_offset_table. This is related to CVE-2017-5753. Signed-off-by: Andrew Honig Reviewed-by: Jim Mattson Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/vmx.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 91ae4e2..ee766c2 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -858,8 +858,16 @@ static inline short vmcs_field_to_offset(unsigned long field) { BUILD_BUG_ON(ARRAY_SIZE(vmcs_field_to_offset_table) > SHRT_MAX); - if (field >= ARRAY_SIZE(vmcs_field_to_offset_table) || - vmcs_field_to_offset_table[field] == 0) + if (field >= ARRAY_SIZE(vmcs_field_to_offset_table)) + return -ENOENT; + + /* + * FIXME: Mitigation for CVE-2017-5753. To be replaced with a + * generic mechanism. + */ + asm("lfence"); + + if (vmcs_field_to_offset_table[field] == 0) return -ENOENT; return vmcs_field_to_offset_table[field]; -- 2.7.4