Re: [PATCH] Security/sysfs: v2 - Enable security xattrs to be set on sysfs files, directories, and symlinks.

[Stephen Smalley <sds@tycho.nsa.gov>]

On Wed, 2009-08-19 at 19:41 -0700, Eric W. Biederman wrote:
> Casey Schaufler <casey@schaufler-ca.com> writes:
> 
> > So I still don't like the way it exposes LSM internal data to the
> > file system code, but given how long it's taking for me to create
> > a better solution I don't think that I can in all fairness say NAK
> > to David Quigley's sysfs patch any longer. I withdraw my objection,
> > while maintaining my reservations.
> 
> Until I see it wired up against another filesystem I retain my
> objections.  When I asked he pretty much told me that it doesn't
> generalize to other filesystems well and it is a sysfs special case.

I think that's a misunderstanding (likely our fault).  As I said, we
already have what we need for getting and setting security xattrs on
in-memory filesystems that pin their inodes, so the only missing bit was
the ability to preserve userspace-set attributes in in-memory
filesystems that can evict their inodes.  And the hooks proposed by
David are generic for that purpose.   You still have to add them to each
such in-memory filesystem that doesn't pin its inodes as each has its
own distinct backing data structure, but you don't need more hooks or a
different approach.

> The way sysctl and proc are wired as special cases into the lsm
> has been a maintenance disaster so far, and I think it a very bad
> idea to add yet another lsm special case, that supports only one
> filesystem.

-- 
Stephen Smalley
National Security Agency