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Date: Wed, 5 Oct 2016 23:05:18 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Kees Cook <keescook@...omium.org>
Cc: Andy Lutomirski <luto@...capital.net>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Alexei Starovoitov <ast@...nel.org>, Arnd Bergmann <arnd@...db.de>,
Casey Schaufler <casey@...aufler-ca.com>,
Daniel Borkmann <daniel@...earbox.net>,
Daniel Mack <daniel@...que.org>, David Drysdale <drysdale@...gle.com>,
"David S . Miller"
<davem@...emloft.net>,
Elena Reshetova <elena.reshetova@...el.com>,
"Eric W . Biederman" <ebiederm@...ssion.com>,
James Morris <james.l.morris@...cle.com>,
Paul Moore <pmoore@...hat.com>, Sargun Dhillon <sargun@...gun.me>,
"Serge E . Hallyn" <serge@...lyn.com>, Tejun Heo <tj@...nel.org>,
Will Drewry <wad@...omium.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
Linux API <linux-api@...r.kernel.org>,
LSM List <linux-security-module@...r.kernel.org>,
Network Development <netdev@...r.kernel.org>,
"open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC v3 11/22] seccomp,landlock: Handle Landlock hooks per
process hierarchy
On 04/10/2016 01:52, Kees Cook wrote:
> On Wed, Sep 14, 2016 at 3:34 PM, Mickaël Salaün <mic@...ikod.net> wrote:
>>
>> On 14/09/2016 20:43, Andy Lutomirski wrote:
>>> On Wed, Sep 14, 2016 at 12:24 AM, Mickaël Salaün <mic@...ikod.net> wrote:
>>>> A Landlock program will be triggered according to its subtype/origin
>>>> bitfield. The LANDLOCK_FLAG_ORIGIN_SECCOMP value will trigger the
>>>> Landlock program when a seccomp filter will return RET_LANDLOCK.
>>>> Moreover, it is possible to return a 16-bit cookie which will be
>>>> readable by the Landlock programs in its context.
>>>
>>> Are you envisioning that the filters will return RET_LANDLOCK most of
>>> the time or rarely? If it's most of the time, then maybe this could
>>> be simplified a bit by unconditionally calling the landlock filter and
>>> letting the landlock filter access a struct seccomp_data if needed.
>>
>> Exposing seccomp_data in a Landlock context may be a good idea. The main
>> implication is that Landlock programs may then be architecture specific
>> (if dealing with data) as seccomp filters are. Another point is that it
>> remove any direct binding between seccomp filters and Landlock programs.
>> I will try this (more simple) approach.
>
> Yeah, I would prefer that the seccomp code isn't doing list management
> to identify the landlock hooks to trigger, etc. I think that's better
> done on the LSM side. And since multiple seccomp filters could trigger
> landlock, it may be best to just leave the low 16 bits unused
> entirely. Then all state management is handled by the landlock eBPF
> maps, not a value coming from seccomp that can get stomped on by new
> filters, etc.
Right, this approach should be simpler, more efficient and independent
from seccomp. This will be in the next RFC.
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