From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: Re: [PATCH v4 0/2] Add further ioctl() operations for namespace discovery Date: Wed, 25 Jan 2017 15:28:27 +1300 Message-ID: <87tw8nkh4k.fsf@xmission.com> References: <93e5c7f9-9dc1-6c93-ad20-0ba053d8bfef@gmail.com> <963f76f9-3ae5-b316-e688-00d3e59cad30@gmail.com> <87d1fblx2s.fsf@xmission.com> <877f5jlvs1.fsf@xmission.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <877f5jlvs1.fsf@xmission.com> (Eric W. Biederman's message of "Wed, 25 Jan 2017 15:26:38 +1300") Sender: linux-kernel-owner@vger.kernel.org To: "Michael Kerrisk (man-pages)" Cc: "Serge E. Hallyn" , Linux API , lkml , "linux-fsdevel@vger.kernel.org" , Andrey Vagin , James Bottomley , "W. Trevor King" , Alexander Viro List-Id: linux-api@vger.kernel.org ebiederm@xmission.com (Eric W. Biederman) writes: > "Michael Kerrisk (man-pages)" writes: > >> Hi Eric, >> >> On 25 January 2017 at 14:58, Eric W. Biederman wrote: >>> "Michael Kerrisk (man-pages)" writes: >>> >>>> I would like to write code that discovers the namespace setup on a live >>>> system. The NS_GET_PARENT and NS_GET_USERNS ioctl() operations added in >>>> Linux 4.9 provide much of what I want, but there are still a couple of >>>> small pieces missing. Those pieces are added with this patch series. >>> >>> So it looks like the -EOVERFLOW change broke your example program. >>> Causing it to abort if -EOVERFLOW is hit. Do we really want to return >>> -EOVERFLOW? Or do you want to fix your program? >> >> Bother! Yes, I should have kept the example program in sync. (I >> overlooked that it was not any more in sync.) >> >> So, I want to make sure I understand correctly, before I aswer your >> question. Suppose we have >> >> 1. Outer namespace owned by UID 0 >> 2. Inner namespace owned by UID 1000 >> 3. A UID mapping in the inner namespace that maps '0 1000 1' >> 4. A processs, X, in the outer namespace with UID 0 (and all caps). >> >> That's the case you're meaning, right? > > I think so I just noticed you did not handle -EOVERFLOW in > the one NS_GET_OWNER_UID call. > >> So, UID 0 doesn't have a >> mapping into the inner namespace, but does have all capabilities in >> that inner namespace, right? > > That is correct. My concern is that the difference between returning -EOVERFLOW and overflow_uid is primarily about usability. If you haven't played with the usability I don't trust that we have made the proper trade off. Eric From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from out01.mta.xmission.com ([166.70.13.231]:55779 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750984AbdAYCcs (ORCPT ); Tue, 24 Jan 2017 21:32:48 -0500 From: ebiederm@xmission.com (Eric W. Biederman) To: "Michael Kerrisk \(man-pages\)" Cc: "Serge E. Hallyn" , Linux API , lkml , "linux-fsdevel\@vger.kernel.org" , Andrey Vagin , James Bottomley , "W. Trevor King" , Alexander Viro References: <93e5c7f9-9dc1-6c93-ad20-0ba053d8bfef@gmail.com> <963f76f9-3ae5-b316-e688-00d3e59cad30@gmail.com> <87d1fblx2s.fsf@xmission.com> <877f5jlvs1.fsf@xmission.com> Date: Wed, 25 Jan 2017 15:28:27 +1300 In-Reply-To: <877f5jlvs1.fsf@xmission.com> (Eric W. Biederman's message of "Wed, 25 Jan 2017 15:26:38 +1300") Message-ID: <87tw8nkh4k.fsf@xmission.com> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [PATCH v4 0/2] Add further ioctl() operations for namespace discovery Sender: linux-fsdevel-owner@vger.kernel.org List-ID: ebiederm@xmission.com (Eric W. Biederman) writes: > "Michael Kerrisk (man-pages)" writes: > >> Hi Eric, >> >> On 25 January 2017 at 14:58, Eric W. Biederman wrote: >>> "Michael Kerrisk (man-pages)" writes: >>> >>>> I would like to write code that discovers the namespace setup on a live >>>> system. The NS_GET_PARENT and NS_GET_USERNS ioctl() operations added in >>>> Linux 4.9 provide much of what I want, but there are still a couple of >>>> small pieces missing. Those pieces are added with this patch series. >>> >>> So it looks like the -EOVERFLOW change broke your example program. >>> Causing it to abort if -EOVERFLOW is hit. Do we really want to return >>> -EOVERFLOW? Or do you want to fix your program? >> >> Bother! Yes, I should have kept the example program in sync. (I >> overlooked that it was not any more in sync.) >> >> So, I want to make sure I understand correctly, before I aswer your >> question. Suppose we have >> >> 1. Outer namespace owned by UID 0 >> 2. Inner namespace owned by UID 1000 >> 3. A UID mapping in the inner namespace that maps '0 1000 1' >> 4. A processs, X, in the outer namespace with UID 0 (and all caps). >> >> That's the case you're meaning, right? > > I think so I just noticed you did not handle -EOVERFLOW in > the one NS_GET_OWNER_UID call. > >> So, UID 0 doesn't have a >> mapping into the inner namespace, but does have all capabilities in >> that inner namespace, right? > > That is correct. My concern is that the difference between returning -EOVERFLOW and overflow_uid is primarily about usability. If you haven't played with the usability I don't trust that we have made the proper trade off. Eric