From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.hallyn.com (mail.hallyn.com [178.63.66.53]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3ED1A68 for ; Sun, 28 Nov 2021 15:18:08 +0000 (UTC) Received: by mail.hallyn.com (Postfix, from userid 1001) id 12891A17; Sun, 28 Nov 2021 09:18:06 -0600 (CST) Date: Sun, 28 Nov 2021 09:18:06 -0600 From: "Serge E. Hallyn" To: James Bottomley Cc: "Serge E. Hallyn" , linux-integrity@vger.kernel.org, containers@lists.linux.dev, Mimi Zohar , Dmitry Kasatkin , Stefan Berger , "Eric W . Biederman" , krzysztof.struczynski@huawei.com, Roberto Sassu , Michael Peters , Luke Hinds , Lily Sturmann , Patrick Uiterwijk , Christian Brauner Subject: Re: [RFC 1/3] userns: add uuid field Message-ID: <20211128151805.GA15306@mail.hallyn.com> References: <20211127164549.2571457-1-James.Bottomley@HansenPartnership.com> <20211127164549.2571457-2-James.Bottomley@HansenPartnership.com> <20211128044558.GA11794@mail.hallyn.com> <2e32a6897877ed600de64b3d664dc6014389dbe4.camel@HansenPartnership.com> Precedence: bulk X-Mailing-List: containers@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2e32a6897877ed600de64b3d664dc6014389dbe4.camel@HansenPartnership.com> User-Agent: Mutt/1.9.4 (2018-02-28) On Sun, Nov 28, 2021 at 08:29:21AM -0500, James Bottomley wrote: > On Sat, 2021-11-27 at 22:45 -0600, Serge E. Hallyn wrote: > > On Sat, Nov 27, 2021 at 04:45:47PM +0000, James Bottomley wrote: > > > As a precursor to namespacing IMA a way of uniquely identifying the > > > namespace to appear in the IMA log is needed. This log may be > > > transported away from the running system and may be analyzed even > > > after the system has been rebooted. Thus we need a way of > > > identifying namespaces in the log which is unique. UUID, being > > > designed probabilistically never to repeat, fits this bill so add > > > it to the user_namespace which we'll also use for namespacing IMA. > > > > If the logs run across 5 boots, is it important to you that the > > uuid be unique across all 5 boots? Would it suffice to have a > > per-boot unique count and report that plus some indicator of the > > current boot (like boot time in jiffies)? > > For the purposes of IMA it's only really important to have the uuid be > unique within the particular log ... i.e. unique per boot. However, > given the prevalence of uuids elsewhere and the fact we have no current > per-boot unique label for the namespace (the inode number could > repeat), it seemed reasonable to employ uuids for this rather than > invent a different identifier. Plus IMA isn't going to complain if we > have a globally unique identifier ... Ok - Note I'm not saying I heavily object, but I'm mildly concerned about users who happen to spin off a lot of user namespaces for quick jobs being penalized. I suspect Eric will also worry about the namespacing implications - i.e. people *will* want to start restoring user namespaces with a previously used uuid. So given that 'unique per boot' is sufficient, what would be the problem with simply adding a simple ever-increasing unique atomix count to the struct user_namespace? -serge