[Dev] Smack and xattr relationship - raw flash

Schaufler, Casey casey.schaufler at intel.com
Wed May 28 16:20:39 GMT 2014


> -----Original Message-----
> From: Counihan, Tom
> Sent: Wednesday, May 28, 2014 6:55 AM
> To: Schaufler, Casey; dev at lists.tizen.org
> Subject: RE: Smack and xattr relationship - raw flash
> 
> Many thanks Casey,
> I think I get it - for fs with no xattrs, I get a more coarse grained control
> against all files in that filesystem, controlled identically as per the Smack
> labelled on the fs itself.

That is correct.

> Ubifs needs more attention on my side to see if claims match expectations.

Let me know what you discover.

> > -----Original Message-----
> > From: Schaufler, Casey
> > Sent: Wednesday, May 28, 2014 2:44 PM
> > To: Counihan, Tom; dev at lists.tizen.org
> > Subject: RE: Smack and xattr relationship - raw flash
> >
> > > -----Original Message-----
> > > From: Dev [mailto:dev-bounces at lists.tizen.org] On Behalf Of
> > > Counihan, Tom
> > > Sent: Wednesday, May 28, 2014 3:31 AM
> > > To: dev at lists.tizen.org
> > > Subject: [Dev] Smack and xattr relationship - raw flash
> > >
> > > Hi Folks,
> > >
> > > Here: http://schaufler-ca.com/description_from_the_linux_source_tree
> > > I
> > > read:
> > > " It requires netlabel and works best with file systems that support
> > > extended attributes, although xattr support is not strictly required".
> > >
> > > I'm curious to learn more the scalability of Smack across filesystems.
> > > The 'not strictly' statement implies a non-issue.
> > > What if my device uses raw flash - will for example ubifs work with
> > > Smack as comprehensively as say ext4 on a block device?
> >
> > Filesystems that don't support xattrs can be used with Smack, but
> > files cannot be labeled individually. Instead, mount options
> > (smackfsroot and
> > smackfsdefault) are used to specify the Smack labels of all the files
> > on the filesystem. You could construct a system using only
> > single-label filesystems if you had to.
> >
> > I have not tried the xattr support in ubifs, but the literature claims
> > that it is "much improved" as of early last year. If the xattr support
> > in ubifs functions properly you will be able to use it instead of ext4.
> >
> >
> >
> > > Warm Regards
> > > Tom.
> > >
> > >
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