Re: [RFC 1/3] userns: add uuid field

[James Bottomley <James.Bottomley@HansenPartnership.com>]

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 ...

James