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    Subject[ 002/117] KVM: Ensure all vcpus are consistent with in-kernel irqchip settings
    3.2-stable review patch.  If anyone has any objections, please let me know.

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

    From: Marcelo Tosatti <mtosatti@redhat.com>

    From: Avi Kivity <avi@redhat.com>

    (cherry picked from commit 3e515705a1f46beb1c942bb8043c16f8ac7b1e9e)

    If some vcpus are created before KVM_CREATE_IRQCHIP, then
    irqchip_in_kernel() and vcpu->arch.apic will be inconsistent, leading
    to potential NULL pointer dereferences.

    Fix by:
    - ensuring that no vcpus are installed when KVM_CREATE_IRQCHIP is called
    - ensuring that a vcpu has an apic if it is installed after KVM_CREATE_IRQCHIP

    This is somewhat long winded because vcpu->arch.apic is created without
    kvm->lock held.

    Based on earlier patch by Michael Ellerman.

    Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
    Signed-off-by: Avi Kivity <avi@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    arch/ia64/kvm/kvm-ia64.c | 5 +++++
    arch/x86/kvm/x86.c | 8 ++++++++
    include/linux/kvm_host.h | 7 +++++++
    virt/kvm/kvm_main.c | 4 ++++
    4 files changed, 24 insertions(+), 0 deletions(-)

    diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
    index 43f4c92..7073185 100644
    --- a/arch/ia64/kvm/kvm-ia64.c
    +++ b/arch/ia64/kvm/kvm-ia64.c
    @@ -1169,6 +1169,11 @@ out:

    #define PALE_RESET_ENTRY 0x80000000ffffffb0UL

    +bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu)
    +{
    + return irqchip_in_kernel(vcpu->kcm) == (vcpu->arch.apic != NULL);
    +}
    +
    int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
    {
    struct kvm_vcpu *v;
    diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    index e04cae1..4fc5323 100644
    --- a/arch/x86/kvm/x86.c
    +++ b/arch/x86/kvm/x86.c
    @@ -3579,6 +3579,9 @@ long kvm_arch_vm_ioctl(struct file *filp,
    r = -EEXIST;
    if (kvm->arch.vpic)
    goto create_irqchip_unlock;
    + r = -EINVAL;
    + if (atomic_read(&kvm->online_vcpus))
    + goto create_irqchip_unlock;
    r = -ENOMEM;
    vpic = kvm_create_pic(kvm);
    if (vpic) {
    @@ -6486,6 +6489,11 @@ void kvm_arch_check_processor_compat(void *rtn)
    kvm_x86_ops->check_processor_compatibility(rtn);
    }

    +bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu)
    +{
    + return irqchip_in_kernel(vcpu->kvm) == (vcpu->arch.apic != NULL);
    +}
    +
    int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
    {
    struct page *page;
    diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
    index 35410ef..6136821 100644
    --- a/include/linux/kvm_host.h
    +++ b/include/linux/kvm_host.h
    @@ -744,6 +744,13 @@ static inline bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu)
    {
    return vcpu->kvm->bsp_vcpu_id == vcpu->vcpu_id;
    }
    +
    +bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu);
    +
    +#else
    +
    +static inline bool kvm_vcpu_compatible(struct kvm_vcpu *vcpu) { return true; }
    +
    #endif

    #ifdef __KVM_HAVE_DEVICE_ASSIGNMENT
    diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    index 9ffac2e..ec747dc 100644
    --- a/virt/kvm/kvm_main.c
    +++ b/virt/kvm/kvm_main.c
    @@ -1667,6 +1667,10 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
    goto vcpu_destroy;

    mutex_lock(&kvm->lock);
    + if (!kvm_vcpu_compatible(vcpu)) {
    + r = -EINVAL;
    + goto unlock_vcpu_destroy;
    + }
    if (atomic_read(&kvm->online_vcpus) == KVM_MAX_VCPUS) {
    r = -EINVAL;
    goto unlock_vcpu_destroy;



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