Re: [PATCH v30 12/12] landlock: Add user and kernel documentation

[Mickaël Salaün]

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@xxxxxxxxxxxxxxxxxxx>
[...]
>>
>>> [...]
>>> +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. :)