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From:   Maxim Levitsky <mlevitsk@redhat.com>
To:     kvm@vger.kernel.org
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-kernel@vger.kernel.org,
        Chenyi Qiang <chenyi.qiang@intel.com>,
        Yang Zhong <yang.zhong@intel.com>, x86@kernel.org,
        Shuah Khan <shuah@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Maxim Levitsky <mlevitsk@redhat.com>,
        Colton Lewis <coltonlewis@google.com>,
        Borislav Petkov <bp@alien8.de>, Peter Xu <peterx@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Jim Mattson <jmattson@google.com>,
        linux-kselftest@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
        Wei Wang <wei.w.wang@intel.com>,
        David Matlack <dmatlack@google.com>, stable@vger.kernel.org
Subject: [PATCH v2 2/9] KVM: x86: nSVM: harden svm_free_nested against freeing vmcb02 while still in use
Date:   Thu,  3 Nov 2022 16:13:44 +0200
Message-Id: <20221103141351.50662-3-mlevitsk@redhat.com>
In-Reply-To: <20221103141351.50662-1-mlevitsk@redhat.com>
References: <20221103141351.50662-1-mlevitsk@redhat.com>
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Make sure that KVM uses vmcb01 before freeing nested state, and warn if
that is not the case.

This is a minimal fix for CVE-2022-3344 making the kernel print a warning
instead of a kernel panic.

Cc: stable@vger.kernel.org
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
---
 arch/x86/kvm/svm/nested.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index b258d6988f5dde..b74da40c1fc40c 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1126,6 +1126,9 @@ void svm_free_nested(struct vcpu_svm *svm)
 	if (!svm->nested.initialized)
 		return;
 
+	if (WARN_ON_ONCE(svm->vmcb != svm->vmcb01.ptr))
+		svm_switch_vmcb(svm, &svm->vmcb01);
+
 	svm_vcpu_free_msrpm(svm->nested.msrpm);
 	svm->nested.msrpm = NULL;
 
-- 
2.34.3