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Date: Thu, 09 Feb 2017 07:43:25 -0700
From: "Jan Beulich" <JBeulich@suse.com>
To: "Paul Durrant" <paul.durrant@citrix.com>
Cc: <xen-devel@lists.xenproject.org>,
        "Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
        "Juergen Gross" <JGross@suse.com>, <linux-kernel@vger.kernel.org>
Subject: Re: [Xen-devel] [PATCH 3/3] xen/privcmd: add
 IOCTL_PRIVCMD_RESTRICT
References: <1486649866-4869-1-git-send-email-paul.durrant@citrix.com>
 <1486649866-4869-4-git-send-email-paul.durrant@citrix.com>
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>>> On 09.02.17 at 15:17, <paul.durrant@citrix.com> wrote:
> @@ -666,6 +680,20 @@ static long privcmd_ioctl_dm_op(void __user *udata)
>  	return rc;
>  }
>  
> +static long privcmd_ioctl_restrict(struct file *file, void __user *udata)
> +{
> +	struct privcmd_data *data = file->private_data;
> +	domid_t dom;
> +
> +	if (copy_from_user(&dom, udata, sizeof(dom)))
> +		return -EFAULT;
> +
> +	/* Set restriction to the specified domain */
> +	data->domid = dom;
> +
> +	return 0;
> +}

Is it really intended for the caller to be able to undo this, by passing
in DOMID_INVALID?

Jan