Re: [PATCH v28 07/12] landlock: Support filesystem access-control

[Serge E. Hallyn]

On Wed, Feb 10, 2021 at 09:17:25PM +0100, Mickaël Salaün wrote:
> 
> On 10/02/2021 20:36, Serge E. Hallyn wrote:
> > On Tue, Feb 02, 2021 at 05:27:05PM +0100, Mickaël Salaün wrote:
> >> From: Mickaël Salaün <mic@xxxxxxxxxxxxxxxxxxx>
> >>
> >> Thanks to the Landlock objects and ruleset, it is possible to identify
> >> inodes according to a process's domain.  To enable an unprivileged
> > 
> > This throws me off a bit.  "identify inodes according to a process's domain".
> > What exactly does it mean?  "identify" how ?
> 
> A domain is a set of rules (i.e. layers of rulesets) enforced on a set
> of threads. Inodes are tagged per domain (i.e. not system-wide) and
> actions are restricted thanks to these tags, which form rules. It means
> that the created access-controls are scoped to a set of threads.

Thanks, that's helpful.  To me it would be much clearer if you used the word
'tagged' :

  Using the Landlock objects and ruleset, it is possible to tag inodes
  according to a process's domain.

> >> process to express a file hierarchy, it first needs to open a directory
> >> (or a file) and pass this file descriptor to the kernel through
> >> landlock_add_rule(2).  When checking if a file access request is
> >> allowed, we walk from the requested dentry to the real root, following
> >> the different mount layers.  The access to each "tagged" inodes are
> >> collected according to their rule layer level, and ANDed to create
> >> access to the requested file hierarchy.  This makes possible to identify
> >> a lot of files without tagging every inodes nor modifying the
> >> filesystem, while still following the view and understanding the user
> >> has from the filesystem.
> >>
> >> Add a new ARCH_EPHEMERAL_INODES for UML because it currently does not
> >> keep the same struct inodes for the same inodes whereas these inodes are
> >> in use.
> > 
> > -serge
> >