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    SubjectRe: [PATCH v4 RESEND 1/5] KVM: x86: hyperv: enforce vp_index < KVM_MAX_VCPUS
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    On 22/08/2018 12:18, Vitaly Kuznetsov wrote:
    > Hyper-V TLFS (5.0b) states:
    >
    >> Virtual processors are identified by using an index (VP index). The
    >> maximum number of virtual processors per partition supported by the
    >> current implementation of the hypervisor can be obtained through CPUID
    >> leaf 0x40000005. A virtual processor index must be less than the
    >> maximum number of virtual processors per partition.
    >
    > Forbid userspace to set VP_INDEX above KVM_MAX_VCPUS. get_vcpu_by_vpidx()
    > can now be optimized to bail early when supplied vpidx is >= KVM_MAX_VCPUS.
    >
    > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
    > Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
    > ---
    > arch/x86/kvm/hyperv.c | 8 +++++---
    > 1 file changed, 5 insertions(+), 3 deletions(-)
    >
    > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
    > index 01d209ab5481..0cd597b0f754 100644
    > --- a/arch/x86/kvm/hyperv.c
    > +++ b/arch/x86/kvm/hyperv.c
    > @@ -132,8 +132,10 @@ static struct kvm_vcpu *get_vcpu_by_vpidx(struct kvm *kvm, u32 vpidx)
    > struct kvm_vcpu *vcpu = NULL;
    > int i;
    >
    > - if (vpidx < KVM_MAX_VCPUS)
    > - vcpu = kvm_get_vcpu(kvm, vpidx);
    > + if (vpidx >= KVM_MAX_VCPUS)
    > + return NULL;
    > +
    > + vcpu = kvm_get_vcpu(kvm, vpidx);
    > if (vcpu && vcpu_to_hv_vcpu(vcpu)->vp_index == vpidx)
    > return vcpu;
    > kvm_for_each_vcpu(i, vcpu, kvm)
    > @@ -1044,7 +1046,7 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
    >
    > switch (msr) {
    > case HV_X64_MSR_VP_INDEX:
    > - if (!host)
    > + if (!host || (u32)data >= KVM_MAX_VCPUS)
    > return 1;
    > hv->vp_index = (u32)data;
    > break;
    >

    Queued, thanks.

    Paolo

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