KVM: x86: nSVM: harden svm_free_nested against freeing vmcb02 while still in use

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>
Message-Id: <20221103141351.50662-3-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 4c62099..b02a3a1 100644 (file)
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1125,6 +1125,9 @@ 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;