From: Justin Suess <utilityemal77@gmail.com>
To: Paul Moore <paul@paul-moore.com>
Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org,
kpsingh@kernel.org, mic@digikod.net, viro@zeniv.linux.org.uk,
brauner@kernel.org, kees@kernel.org, gnoack@google.com,
jack@suse.cz, song@kernel.org, yonghong.song@linux.dev,
martin.lau@linux.dev, m@maowtm.org, bpf@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH bpf-next 00/13] BPF interface for applying Landlock rulesets
Date: Fri, 31 Jul 2026 17:15:20 -0400 [thread overview]
Message-ID: <am0JT2UJQgl0ogwy@zenbox> (raw)
In-Reply-To: <CAHC9VhSSzNBCSvy4cQHh6OOM4-EvHF+bmrB9=V1y=Lj53RvxQQ@mail.gmail.com>
On Fri, Jul 31, 2026 at 04:30:39PM -0400, Paul Moore wrote:
> On Thu, Jul 30, 2026 at 10:21 PM Justin Suess <utilityemal77@gmail.com> wrote:
> >
> > Howdy,
> >
> > This series lets BPF programs apply an existing, userspace-created
> > Landlock ruleset to a program during exec. The goal is unchanged from
> > the RFC [1]: BPF does not create, inspect, or mutate Landlock policy,
> > it only decides whether a ruleset that was already created and
> > validated through Landlock's existing userspace API should be applied,
> > based on runtime exec context.
> >
> > Motivation
> > ---
> > Deploying Landlock today requires the sandboxed program's
> > cooperation. A process can only restrict itself, so applying a
> > policy system-wide means wrapping every launch path with a helper
> > that calls landlock_restrict_self(2) before exec, and anything
> > spawned outside those wrappers runs unconfined. Supervising exec
> > from userspace instead (ptrace, seccomp user notifications) is racy
> > and slow. Meanwhile, the tools that do enforce system-wide policy
> > with BPF LSM programs today (container security agents such as
> > KubeArmor and Tetragon) end up reimplementing path-based access
> > control in BPF, fraught with horrors of path reconstruction, bind
> > mounts, rename races, and worse, which is exactly the problem Landlock
> > already solves in the kernel, with maintained and versioned semantics.
> >
> > This series composes BPF and Landlock along their natural grain. The
> > intended deployment: a supervisor creates one ruleset per policy
> > class through the existing syscalls, a syscall BPF program parks
> > them in map kptr fields, and an LSM BPF program picks which (if
> > any) to apply to an execution based on its runtime context. The
> > policy semantics stay Landlock's; BPF contributes only the
> > programmable decision of when and to whom. Deciding inside the
> > exec path closes the race a userspace supervisor cannot: the
> > policy is in place before the first instruction of the new program
> > runs.
>
> Discretionary models are fun, and useful in certain situations, but
> they do have their limitations ;) To be fair, mandatory models have
> their limitations too :)
>
This series does kind of blur the lines between DAC and MAC
a little... interesting thought.
> I've only just barely skimmed some of the patches in this patchset,
> and I didn't have a chance to fully read your reply in the previous
> revision yet, so I wanted to get you a quick response here ... as
> incomplete as it may be.
>
> As you may, or may not have seen, there is currently an ongoing debate
> regarding the location of LSM kfuncs that will impact this patchset.
> Sadly, we don't appear to be approaching an agreement on this issue
> which introduces some additional risk to this patchset. We'll have to
> see how that ends up, but I just wanted you to be aware of the
> situation.
>
I'll hold off on further iterations until that's resolved.
Moving these kfuncs anywhere fortunately amounts to a trivial
cut/paste on end anyway.
> I need to look closer at both the LSM hooks and the BPF kfuncs before
> I can really definitively comment on them. It looks like there has
> been some progress towards an LSM agnostic interface, but I'm
> concerned more work might be needed. However, as I said earlier, a
> closer examination is needed and perhaps that will reveal something
> different.
>
> It's also worth mentioning that this functionality looks an awful lot
> like a call to lsm_set_self_attr(LSM_ATTR_EXEC,
> <lsm_ctx:LSM_ID_LANDLOCK>, size, 0) with a lsm_ctx::ctx set to a
> policy fd. Once again, perhaps a closer inspection will reveal that
> it is nothing like that, but it kept popping into my head while
> reading things so I wanted to mention it, especially as it a lot of
> the framework infrastructure already exists.
They were the direct inspiration for the hooks (and set/getprocattr).
Main difference being the object in the hook is a trusted kernel pointer
rather than a lsm_ctx blob or fd. We can't use an fd here since the
sandboxed task and supervisor don't share an fd table.
I'll wait for your full review, no rush.
Justin
>
> --
> paul-moore.com
next prev parent reply other threads:[~2026-07-31 21:15 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-31 2:20 [PATCH bpf-next 00/13] BPF interface for applying Landlock rulesets Justin Suess
2026-07-31 2:20 ` [PATCH bpf-next 01/13] lsm: Add LSM hook security_policy_kptr_from_fd Justin Suess
2026-07-31 2:20 ` [PATCH bpf-next 02/13] lsm: Add LSM hook security_policy_kptr_put Justin Suess
2026-07-31 2:20 ` [PATCH bpf-next 03/13] lsm: Add LSM hook security_bprm_enforce_policy_kptr Justin Suess
2026-07-31 2:20 ` [PATCH bpf-next 04/13] landlock: Expose the ruleset fd lookup to the rest of Landlock Justin Suess
2026-07-31 2:20 ` [PATCH bpf-next 05/13] landlock: Factor the credential restriction out of landlock_restrict_self() Justin Suess
2026-07-31 22:24 ` bot+bpf-ci
2026-07-31 2:20 ` [PATCH bpf-next 06/13] landlock: Implement the LSM policy kptr hooks Justin Suess
2026-07-31 2:20 ` [PATCH bpf-next 07/13] bpf: Add the LSM policy kfunc infrastructure Justin Suess
2026-07-31 22:24 ` bot+bpf-ci
2026-07-31 2:20 ` [PATCH bpf-next 08/13] bpf: Add the bpf_landlock_put_ruleset kfunc and ruleset destructor Justin Suess
2026-07-31 2:20 ` [PATCH bpf-next 09/13] bpf: Add the bpf_landlock_get_ruleset_from_fd kfunc Justin Suess
2026-07-31 2:20 ` [PATCH bpf-next 10/13] bpf: Add the bpf_landlock_restrict_binprm kfunc Justin Suess
2026-07-31 2:20 ` [PATCH bpf-next 11/13] selftests/bpf: Add tests for the Landlock policy kfuncs Justin Suess
2026-07-31 2:20 ` [PATCH bpf-next 12/13] landlock: Document the BPF kfunc interface Justin Suess
2026-07-31 2:20 ` [PATCH bpf-next 13/13] lsm: Document the LSM policy kptr hooks Justin Suess
2026-07-31 20:30 ` [PATCH bpf-next 00/13] BPF interface for applying Landlock rulesets Paul Moore
2026-07-31 21:15 ` Justin Suess [this message]
2026-07-31 21:28 ` Paul Moore
2026-08-05 21:37 ` Justin Suess
2026-08-05 21:49 ` Justin Suess
2026-08-05 22:51 ` Paul Moore
2026-08-06 0:32 ` Justin Suess
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