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    Subject[PATCH 3.2 097/140] KVM: x86: Add memory barrier on vmcs field lookup
    3.2.100-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Andrew Honig <ahonig@google.com>

    commit 75f139aaf896d6fdeec2e468ddfa4b2fe469bf40 upstream.

    This adds a memory barrier when performing a lookup into
    the vmcs_field_to_offset_table. This is related to
    CVE-2017-5753.

    Signed-off-by: Andrew Honig <ahonig@google.com>
    Reviewed-by: Jim Mattson <jmattson@google.com>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    [bwh: Backported to 3.2: adjust context]
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    --- a/arch/x86/kvm/vmx.c
    +++ b/arch/x86/kvm/vmx.c
    @@ -573,8 +573,18 @@ static const int max_vmcs_field = ARRAY_

    static inline short vmcs_field_to_offset(unsigned long field)
    {
    - if (field >= max_vmcs_field || vmcs_field_to_offset_table[field] == 0)
    + if (field >= max_vmcs_field)
    return -1;
    +
    + /*
    + * FIXME: Mitigation for CVE-2017-5753. To be replaced with a
    + * generic mechanism.
    + */
    + asm("lfence");
    +
    + if (vmcs_field_to_offset_table[field] == 0)
    + return -1;
    +
    return vmcs_field_to_offset_table[field];
    }

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