[PATCH] KVM: nVMX: Trap unconditionally if msr bitmap access fails

[Jan Kiszka <jan.kiszka@siemens.com>]

This avoids basing decisions on uninitialized variables, potentially
leaking kernel data to the L1 guest.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
 arch/x86/kvm/vmx.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 2633199..81a25de 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -5991,7 +5991,8 @@ static bool nested_vmx_exit_handled_msr(struct kvm_vcpu *vcpu,
 	/* Then read the msr_index'th bit from this bitmap: */
 	if (msr_index < 1024*8) {
 		unsigned char b;
-		kvm_read_guest(vcpu->kvm, bitmap + msr_index/8, &b, 1);
+		if (kvm_read_guest(vcpu->kvm, bitmap + msr_index/8, &b, 1))
+			return 1;
 		return 1 & (b >> (msr_index & 7));
 	} else
 		return 1; /* let L1 handle the wrong parameter */
-- 
1.7.3.4