Re: [PATCH 3/3] KVM: Expose MSRs to userspace

Andrew Morton
2006-11-17T01:02:14Z

On Thu, 16 Nov 2006 18:04:22 -0000
Avi Kivity <avi@qumranet.com> wrote:

> +static int kvm_dev_ioctl_set_msrs(struct kvm *kvm, struct kvm_msrs *msrs)
> +{
> + struct kvm_vcpu *vcpu;
> + struct kvm_msr_entry *entry, *entries;
> + int rc;
> + u32 size, num_entries, i;
> +
> + if (msrs->vcpu < 0 || msrs->vcpu >= KVM_MAX_VCPUS)
> + return -EINVAL;
> +
> + num_entries = ARRAY_SIZE(msrs_to_save);
> + if (msrs->nmsrs < num_entries) {
> + msrs->nmsrs = num_entries; /* inform actual size */
> + return -EINVAL;
> + }
> +
> + vcpu = vcpu_load(kvm, msrs->vcpu);
> + if (!vcpu)
> + return -ENOENT;
> +
> + size = msrs->nmsrs * sizeof(struct kvm_msr_entry);
> + rc = -E2BIG;
> + if (size > 4096)
> + goto out_vcpu;

Classic mutiplicative overflow bug. Only msrs->nmsrs doesn't get used
again, so there is no bug here. Yet.

> + rc = -ENOMEM;
> + entries = vmalloc(size);
> + if (entries == NULL)
> + goto out_vcpu;
> +
> + rc = -EFAULT;
> + if (copy_from_user(entries, msrs->entries, size))
> + goto out_free;
> +
> + rc = -EINVAL;
> + for (i=0; i<num_entries; i++) {
> + entry = &entries[i];
> + if (set_msr(vcpu, entry->index, entry->data))
> + goto out_free;
> + }
> +
> + rc = 0;
> +out_free:
> + vfree(entries);
> +
> +out_vcpu:
> + vcpu_put(vcpu);
> +
> + return rc;
> +}

This function returns no indication of how many msrs it actually did set.
Should it?