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Date:   Wed, 10 Feb 2021 13:36:24 -0600
From:   "Serge E. Hallyn" <serge@hallyn.com>
To:     =?iso-8859-1?Q?Micka=EBl_Sala=FCn?= <mic@digikod.net>
Cc:     James Morris <jmorris@namei.org>, Jann Horn <jannh@google.com>,
        "Serge E . Hallyn" <serge@hallyn.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Anton Ivanov <anton.ivanov@cambridgegreys.com>,
        Arnd Bergmann <arnd@arndb.de>,
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        Kees Cook <keescook@chromium.org>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Richard Weinberger <richard@nod.at>,
        Shuah Khan <shuah@kernel.org>,
        Vincent Dagonneau <vincent.dagonneau@ssi.gouv.fr>,
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        linux-security-module@vger.kernel.org, x86@kernel.org,
        =?iso-8859-1?Q?Micka=EBl_Sala=FCn?= <mic@linux.microsoft.com>
Subject: Re: [PATCH v28 07/12] landlock: Support filesystem access-control
Message-ID: <20210210193624.GA29893@mail.hallyn.com>
References: <20210202162710.657398-1-mic@digikod.net>
 <20210202162710.657398-8-mic@digikod.net>
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On Tue, Feb 02, 2021 at 05:27:05PM +0100, Micka?l Sala?n wrote:
> From: Micka?l Sala?n <mic@linux.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