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

[Serge E. Hallyn]

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 ?

> 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