Re: [RFC PATCH 08/20] bpf: Add Landlock ruleset map type

[Song Liu]

On Fri, Apr 17, 2026 at 1:33 PM Justin Suess <utilityemal77@xxxxxxxxx> wrote:
[...]
> > > > to the caller) and pass them as file descriptor?
> > > This "pass them as a file descriptor" is the tricky part. It would be
> > > very convenient if we could send the fd to bpf from userspace and have
> > > it be implicitly converted (like in the BPF_MAP_TYPE_LANDLOCK_RULESET
> > > implementation) in one step, but I just don't see a way to do that with
> > > the bpf_landlock_get_ruleset_from_fd kfunc approach.
> >
> > Song's idea to have a generic FD map looks promising.
> >
>
> I agree the generic FD map sounds like a good fit.

Well, I am not 100% sure a generic FD map adds enough value
on top of current __kptr solutions. This will be more tricky if we
have to touch file_operations.

> So this would be three parts like:
>
> 1. The new point-of-no-return flags for NNP and staging domain to
> execution time in Landlock. Selftests and doc updates.
> 2. The generic FD map implementation for bpf. Selftests and doc updates.
> 3. The BPF kfunc implementations for Landlock using the same point-of-no
> return staging. Selftests and doc updates.
>
> The scope of which is probably too big for one series.
>
> Luckily part 1 is pretty close to being done as part of my work for v2
> of this series, and can standalone as a preparatory series for Landlock,
> since it adds flags and features that have utility outside of BPF.
>
> Open for ideas on how to split this up (or even better, for some help in
> implementation or prior works).
>
> I'd like to get some feedback and figue out what this generic fd map
> should look like and get some more eyes on that idea to avoid wasting
> reviewer time on an unsuitable implementation.

I will think more about 2. If it indeed adds good value, the upcoming
LSF/MM/BPF is a good opportunity to move this forward.

In the meanwhile, we still need kfuncs to access landlock ruleset.
Therefore, any work on that front should be useful.

Thanks,
Song