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Date: Wed, 24 Mar 2021 17:21:07 +0100
From: Mickaël Salaün <mic@...ikod.net>
To: Kees Cook <keescook@...omium.org>
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>,
David Howells <dhowells@...hat.com>, Jeff Dike <jdike@...toit.com>,
Jonathan Corbet <corbet@....net>, 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 v30 12/12] landlock: Add user and kernel documentation
On 19/03/2021 19:54, Mickaël Salaün wrote:
>
> On 19/03/2021 19:03, Kees Cook wrote:
>> On Tue, Mar 16, 2021 at 09:42:52PM +0100, Mickaël Salaün wrote:
>>> From: Mickaël Salaün <mic@...ux.microsoft.com>
[...]
>>
>>> [...]
>>> +Special filesystems
>>> +-------------------
>>> +
>>> +Access to regular files and directories can be restricted by Landlock,
>>> +according to the handled accesses of a ruleset. However, files that do not
>>> +come from a user-visible filesystem (e.g. pipe, socket), but can still be
>>> +accessed through /proc/self/fd/, cannot currently be restricted. Likewise,
>>> +some special kernel filesystems such as nsfs, which can be accessed through
>>> +/proc/self/ns/, cannot currently be restricted. For now, these kind of special
>>> +paths are then always allowed. Future Landlock evolutions will enable to
>>> +restrict such paths with dedicated ruleset flags.
>>
>> With this series, can /proc (at the top level) be blocked? (i.e. can a
>> landlock user avoid the weirdness by making /proc/$pid/ unavailable?)
>
> /proc can be blocked, but not /proc/*/ns/* because of disconnected
> roots. I plan to address this.
It is important to note that access to sensitive /proc files such as
ns/* and fd/* are automatically restricted according to domain
hierarchies. I'll add this detail to the documentation. :)
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