linux-kernel - Re: [PATCH v3 2/2] nsfs: Add an ioctl() to return owner UID of a userns

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Date:   Thu, 19 Jan 2017 15:12:42 +1300
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     "W. Trevor King" <wking@...mily.us>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Linux API <linux-api@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Andrey Vagin <avagin@...nvz.org>,
        James Bottomley <James.Bottomley@...senpartnership.com>,
        Alexander Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH v3 2/2] nsfs: Add an ioctl() to return owner UID of a userns

On 17 January 2017 at 14:19, W. Trevor King <wking@...mily.us> wrote:
> On Tue, Jan 17, 2017 at 02:03:29PM +1300, Michael Kerrisk (man-pages) wrote:
>> +     case NS_GET_OWNER_UID:
>> +             if (ns->ops->type != CLONE_NEWUSER)
>> +                     return -EINVAL;
>> +             user_ns = container_of(ns, struct user_namespace, ns);
>> +             argp = (unsigned int __user *) arg;
>> +             uid = from_kuid_munged(current_user_ns(), user_ns->owner);
>> +             return put_user(uid, argp);
>> …
>> +/* Get owner UID for a user namespace */
>> +#define NS_GET_OWNER_UID     _IO(NSIO, 0x4)
>
> The comment here should probably be:
>
>   Get owner UID (in the current user namespace) for a user namespace
>
> or some such, to convey that current_user_ns is being passed to
> from_kuid_munged.

Thanks, Trevor. I'll fix that. From a user-space perspective though
"in the current user namespace" should be "in the caller's user
namespace".

Cheers,

Michael

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/