linux-kernel - [PATCH 5.1 084/115] KVM: nVMX: really fix the size checks on KVM_SET_NESTED

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Date:   Mon, 17 Jun 2019 23:09:44 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.1 084/115] KVM: nVMX: really fix the size checks on KVM_SET_NESTED_STATE

[ Upstream commit db80927ea1977a845230a161df643b48fd1e1ea4 ]

The offset for reading the shadow VMCS is sizeof(*kvm_state)+VMCS12_SIZE,
so the correct size must be that plus sizeof(*vmcs12).  This could lead
to KVM reading garbage data from userspace and not reporting an error,
but is otherwise not sensitive.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kvm/vmx/nested.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 8f6f69c26c35..5fa0c17d0b41 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5467,7 +5467,7 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
 	    vmcs12->vmcs_link_pointer != -1ull) {
 		struct vmcs12 *shadow_vmcs12 = get_shadow_vmcs12(vcpu);
 
-		if (kvm_state->size < sizeof(*kvm_state) + 2 * sizeof(*vmcs12))
+		if (kvm_state->size < sizeof(*kvm_state) + VMCS12_SIZE + sizeof(*vmcs12))
 			return -EINVAL;
 
 		if (copy_from_user(shadow_vmcs12,
-- 
2.20.1