Re: [PATCH] bpf: lirc program type should not require SYS_CAP_ADMIN

[Alexei Starovoitov]

On Fri, Apr 14, 2023 at 3:58 AM Sean Young <sean@xxxxxxxx> wrote:
>
> On Thu, Apr 13, 2023 at 04:54:21PM -0700, Alexei Starovoitov wrote:
> > On Thu, Apr 13, 2023 at 1:28 AM Sean Young <sean@xxxxxxxx> wrote:
> > >
> > > On Wed, Apr 12, 2023 at 04:14:05PM -0700, Alexei Starovoitov wrote:
> > > > On Tue, Apr 11, 2023 at 8:45 AM Sean Young <sean@xxxxxxxx> wrote:
> > > > >
> > > > > Make it possible to load lirc program type with just CAP_BPF.
> > > >
> > > > Is it safe?
> > > > If the user can load with just CAP_BPF the FD to the prog and target_fd
> > > > will allow attach as well.
> > >
> > > Exactly, that's the $1m question of course.
> > >
> > > I think it's safe from a lirc perspective because you need to be able to
> > > open the /dev/lirc0 device in the first place; if you can open it, you
> > > alter all sorts of lirc receiving options already. Changing the IR protocol
> > > decoder is no different in that perspective.
> > >
> > > The other side of course, is it save to load a bpf lirc program as a normal
> > > user. I don't see any issue with this; I guess this depends on whether the
> > > subset of functions in lirc_mode2_func_proto() is safe. I am hoping that
> > > the expert opinion everyone here can help answer that question.
> >
> > That part is fine under CAP_BPF.
> > I don't know how lirc devices are typically setup.
> > If they need root to open them
> > then why bother relaxing bpf loading part?
>
> I'd like to get a point where /dev/lircN can have the same permissions as
> for example /dev/videoN devices: group read/write, so that local users
> don't have to become root to use them.
>
> Without relaxing the bpf side, this seems like a chicken and egg problem
> (tiktaalik and egg?).
>
> Also - the CAP_NET_ADMIN requirement seems completely arbitrary compared
> to other program types.

Yeah. Agree. Could you respin with all these additional details
explaining the motivation and driver permission model?