linux-kernel - [PATCH 4.9 021/206] KVM: x86: reset MMU on KVM_SET_VCPU

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Date:   Tue, 10 Jan 2017 14:35:04 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 4.9 021/206] KVM: x86: reset MMU on KVM_SET_VCPU_EVENTS

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Xiao Guangrong <guangrong.xiao@...ux.intel.com>

commit 6ef4e07ecd2db21025c446327ecf34414366498b upstream.

Otherwise, mismatch between the smm bit in hflags and the MMU role
can cause a NULL pointer dereference.

Signed-off-by: Xiao Guangrong <guangrong.xiao@...ux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kvm/x86.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3036,6 +3036,8 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_
 	memset(&events->reserved, 0, sizeof(events->reserved));
 }
 
+static void kvm_set_hflags(struct kvm_vcpu *vcpu, unsigned emul_flags);
+
 static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
 					      struct kvm_vcpu_events *events)
 {
@@ -3072,10 +3074,13 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_e
 		vcpu->arch.apic->sipi_vector = events->sipi_vector;
 
 	if (events->flags & KVM_VCPUEVENT_VALID_SMM) {
+		u32 hflags = vcpu->arch.hflags;
 		if (events->smi.smm)
-			vcpu->arch.hflags |= HF_SMM_MASK;
+			hflags |= HF_SMM_MASK;
 		else
-			vcpu->arch.hflags &= ~HF_SMM_MASK;
+			hflags &= ~HF_SMM_MASK;
+		kvm_set_hflags(vcpu, hflags);
+
 		vcpu->arch.smi_pending = events->smi.pending;
 		if (events->smi.smm_inside_nmi)
 			vcpu->arch.hflags |= HF_SMM_INSIDE_NMI_MASK;