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    Subject[PATCH 3.5 096/103] KVM: Improve create VCPU parameter (CVE-2013-4587)
    Date
    3.5.7.28 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Andy Honig <ahonig@google.com>

    commit 338c7dbadd2671189cec7faf64c84d01071b3f96 upstream.

    In multiple functions the vcpu_id is used as an offset into a bitfield. Ag
    malicious user could specify a vcpu_id greater than 255 in order to set or
    clear bits in kernel memory. This could be used to elevate priveges in the
    kernel. This patch verifies that the vcpu_id provided is less than 255.
    The api documentation already specifies that the vcpu_id must be less than
    max_vcpus, but this is currently not checked.

    Reported-by: Andrew Honig <ahonig@google.com>
    Signed-off-by: Andrew Honig <ahonig@google.com>
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    virt/kvm/kvm_main.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    index 1b29357..6c6631a 100644
    --- a/virt/kvm/kvm_main.c
    +++ b/virt/kvm/kvm_main.c
    @@ -1698,6 +1698,9 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
    int r;
    struct kvm_vcpu *vcpu, *v;

    + if (id >= KVM_MAX_VCPUS)
    + return -EINVAL;
    +
    vcpu = kvm_arch_vcpu_create(kvm, id);
    if (IS_ERR(vcpu))
    return PTR_ERR(vcpu);
    --
    1.8.3.2


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