linux-kernel - [PATCH] KVM: x86: restrict maximal physical address

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Message-Id: <20161125145105.9508-1-rkrcmar@redhat.com>
Date:   Fri, 25 Nov 2016 15:51:05 +0100
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH] KVM: x86: restrict maximal physical address

The guest could have configured a maximal physical address that exceeds
the host.  Prevent that situation as it could easily lead to a bug.

Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 arch/x86/kvm/cpuid.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 25f0f15fab1a..aed910e9fbed 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -136,7 +136,13 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
 		((best->eax & 0xff00) >> 8) != 0)
 		return -EINVAL;
 
-	/* Update physical-address width */
+
+	/*
+	 * Update physical-address width.
+	 * Make sure that it does not exceed hardware capabilities.
+	 */
+	if (cpuid_query_maxphyaddr(vcpu) > boot_cpu_data.x86_phys_bits)
+		return -EINVAL;
 	vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
 
 	kvm_pmu_refresh(vcpu);
-- 
2.10.2