Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v28 07/12] landlock: Support filesystem access-control
To:     "Serge E. Hallyn" <serge@hallyn.com>
Cc:     James Morris <jmorris@namei.org>, Jann Horn <jannh@google.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>,
        Casey Schaufler <casey@schaufler-ca.com>,
        Jeff Dike <jdike@addtoit.com>,
        Jonathan Corbet <corbet@lwn.net>,
        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>,
        kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org,
        linux-arch@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org,
        linux-security-module@vger.kernel.org, x86@kernel.org,
        =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= <mic@linux.microsoft.com>
References: <20210202162710.657398-1-mic@digikod.net>
 <20210202162710.657398-8-mic@digikod.net>
 <20210210193624.GA29893@mail.hallyn.com>
From:   =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= <mic@digikod.net>
Message-ID: <aeba97b6-37cd-4870-0a40-3e7aa84ebd36@digikod.net>
Date:   Wed, 10 Feb 2021 21:17:25 +0100
User-Agent: 
MIME-Version: 1.0
In-Reply-To: <20210210193624.GA29893@mail.hallyn.com>
Content-Type: text/plain; charset=iso-8859-15
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Precedence: bulk


On 10/02/2021 20:36, Serge E. Hallyn wrote:
> 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 ?

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.

> 
>> 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
>