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

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Message-ID: <20210210193624.GA29893@mail.hallyn.com>
Date:   Wed, 10 Feb 2021 13:36:24 -0600
From:   "Serge E. Hallyn" <serge@...lyn.com>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     James Morris <jmorris@...ei.org>, Jann Horn <jannh@...gle.com>,
        "Serge E . Hallyn" <serge@...lyn.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Arnd Bergmann <arnd@...db.de>,
        Casey Schaufler <casey@...aufler-ca.com>,
        Jeff Dike <jdike@...toit.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Richard Weinberger <richard@....at>,
        Shuah Khan <shuah@...nel.org>,
        Vincent Dagonneau <vincent.dagonneau@....gouv.fr>,
        kernel-hardening@...ts.openwall.com, linux-api@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org,
        linux-security-module@...r.kernel.org, x86@...nel.org,
        Mickaël Salaün <mic@...ux.microsoft.com>
Subject: Re: [PATCH v28 07/12] landlock: Support filesystem access-control

On Tue, Feb 02, 2021 at 05:27:05PM +0100, Mickaël Salaün wrote:
> From: Mickaël Salaün <mic@...ux.microsoft.com>
> 
> 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