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

On Thu, 16 Nov 2006 18:04:22 -0000
Avi Kivity <avi <at> 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?