linux-kernel - [PATCH 1/6] KVM: nSVM: Check the value written to MSR_VM_HSAVE

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Message-Id: <20210628104425.391276-2-vkuznets@redhat.com>
Date:   Mon, 28 Jun 2021 12:44:20 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Cathy Avery <cavery@...hat.com>,
        Emanuele Giuseppe Esposito <eesposit@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Michael Roth <mdroth@...ux.vnet.ibm.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/6] KVM: nSVM: Check the value written to MSR_VM_HSAVE_PA

APM states that #GP is raised upon write to MSR_VM_HSAVE_PA when
the supplied address is not page-aligned or is outside of "maximum
supported physical address for this implementation".
page_address_valid() check seems suitable. Also, forcefully page-align
the address when it's written from VMM.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/svm/svm.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 8834822c00cd..b6f85fd19f96 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2941,7 +2941,10 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 			svm_disable_lbrv(vcpu);
 		break;
 	case MSR_VM_HSAVE_PA:
-		svm->nested.hsave_msr = data;
+		if (!msr->host_initiated && !page_address_valid(vcpu, data))
+			return 1;
+
+		svm->nested.hsave_msr = data & PAGE_MASK;
 		break;
 	case MSR_VM_CR:
 		return svm_set_vm_cr(vcpu, data);
-- 
2.31.1