linux-kernel - Re: [RFC v3 11/22] seccomp,landlock: Handle Landlock hooks per process hierarchy

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Message-ID: <CALCETrXm18nNDY-a+toBEcjKKh+zOCVG0=t3ufkpROOHdqfqJQ@mail.gmail.com>
Date:   Wed, 14 Sep 2016 11:43:54 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     "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>,
        Kees Cook <keescook@...omium.org>,
        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 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.


>
> Only seccomp filters loaded from the same thread and before a Landlock
> program can trigger it through LANDLOCK_FLAG_ORIGIN_SECCOMP. Multiple
> Landlock programs can be triggered by one or more seccomp filters. This
> way, each RET_LANDLOCK (with specific cookie) will trigger all the
> allowed Landlock programs once.

This interface seems somewhat awkward.  Should we not have a way to
atomicaly install a whole pile of landlock filters and associated
seccomp filter all at once?

--Andy