linux-kernel - Re: [PATCH 0/2] namespaces: log namespaces per task

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Date:	Mon, 05 May 2014 16:23:56 -0700
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Serge Hallyn <serge.hallyn@...ntu.com>
CC:	containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, eparis@...hat.com,
	linux-audit@...hat.com, ebiederm@...ssion.com, sgrubb@...hat.com
Subject: Re: [PATCH 0/2] namespaces: log namespaces per task



On May 5, 2014 3:36:38 PM PDT, Serge Hallyn <serge.hallyn@...ntu.com> wrote:
>Quoting James Bottomley (James.Bottomley@...senPartnership.com):
>> On Mon, 2014-05-05 at 22:27 +0000, Serge Hallyn wrote:
>> > Quoting James Bottomley (James.Bottomley@...senPartnership.com):
>> > > On Mon, 2014-05-05 at 17:48 -0400, Richard Guy Briggs wrote:
>> > > > On 14/05/05, Serge E. Hallyn wrote:
>> > > > > Quoting James Bottomley
>(James.Bottomley@...senPartnership.com):
>> > > > > > On Tue, 2014-04-22 at 14:12 -0400, Richard Guy Briggs
>wrote:
>> > > > > > > Questions:
>> > > > > > > Is there a way to link serial numbers of namespaces
>involved in migration of a
>> > > > > > > container to another kernel?  (I had a brief look at
>CRIU.)  Is there a unique
>> > > > > > > identifier for each running instance of a kernel?  Or at
>least some identifier
>> > > > > > > within the container migration realm?
>> > > > > > 
>> > > > > > Are you asking for a way of distinguishing an migrated
>container from an
>> > > > > > unmigrated one?  The answer is pretty much "no" because the
>job of
>> > > > > > migration is to restore to the same state as much as
>possible.
>> > > > > > 
>> > > > > > Reading between the lines, I think your goal is to
>correlate audit
>> > > > > > information across a container migration, right?  Ideally
>the management
>> > > > > > system should be able to cough up an audit trail for a
>container
>> > > > > > wherever it's running and however many times it's been
>migrated?
>> > > > > > 
>> > > > > > In that case, I think your idea of a numeric serial number
>in a dense
>> > > > > > range is wrong.  Because the range is dense you're
>obviously never going
>> > > > > > to be able to use the same serial number across a
>migration.  However,
>> > > > > 
>> > > > > Ah, but I was being silly before, we can actually address
>this pretty
>> > > > > simply.  If we just (for instance) add
>> > > > > /proc/self/ns/{ic,mnt,net,pid,user,uts}_seq containing the
>serial number
>> > > > > for the relevant ns for the task, then criu can dump this
>info at
>> > > > > checkpoint.  Then at restart it can dump an audit message per
>task and
>> > > > > ns saying old_serial=%x,new_serial=%x.  That way the audit
>log reader
>> > > > > can if it cares keep track.
>> > > > 
>> > > > This is the sort of idea I had in mind...
>> > > 
>> > > OK, but I don't understand then why you need a serial number. 
>There are
>> > > plenty of things we preserve across a migration, like namespace
>name for
>> > > instance.  Could you explain what function it performs because I
>think I
>> > > might be missing something.
>> > 
>> > We're looking ahead to a time when audit is namespaced, and a
>container
>> > can keep its own audit logs (without limiting what the host audits
>of
>> > course).  So if a container is auditing suspicious activity by some
>> > task in a sub-namesapce, then the whole parent container gets
>migrated,
>> > after migration we want to continue being able to correlate the
>namespaces.
>> > 
>> > We're also looking at audit trails on a host that is up for years. 
>We
>> > would like every namespace to be uniquely logged there.  That is
>why
>> > inode #s on /proc/self/ns/* are not sufficient, unless we add a
>generation
>> > # (which would end more complicated, not less, than a serial #).
>> 
>> Right, but when the contaner has an audit namespace, that namespace
>has
>> a name,
>
>What ns has a name?

The netns for instance.

>  The audit ns can be tied to 50 pid namespaces, and
>we
>want to log which pidns is responsible for something.
>
>If you mean the pidns has a name, that's the problem...  it does not,
>it
>only has a inode # which may later be re-use.

I still think there's a miscommunication somewhere: I believe you just need a stable id to tie the audit to, so why not just give the audit namespace a name like net?  The id would then be durable across migrations.

>> which CRIU would migrate, so why not use that name for the
>> log .. no need for numbers (unless you make the name a number, of
>> course)?
>> 
>> James
>
>Sorry if I'm being dense...

No I think our assumptions are mismatched. I just can't figure out where.

James

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