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    Subject[PATCH v2 2/9] KVM: x86: nSVM: harden svm_free_nested against freeing vmcb02 while still in use
    Date
    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
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