Re: [PATCH bpf-next v3 08/10] tools/libbpf: Add support for BPF_PROG_TYPE_LSM

[KP Singh]

> On Thu, Jan 23, 2020 at 7:25 AM KP Singh <kpsingh@xxxxxxxxxxxx> wrote:
> >
> > From: KP Singh <kpsingh@xxxxxxxxxx>
> >
> > * Add functionality in libbpf to attach eBPF program to LSM hooks
> > * Lookup the index of the LSM hook in security_hook_heads and pass it in
> >   attr->lsm_hook_idx
> >
> > Signed-off-by: KP Singh <kpsingh@xxxxxxxxxx>
> > Reviewed-by: Brendan Jackman <jackmanb@xxxxxxxxxx>
> > Reviewed-by: Florent Revest <revest@xxxxxxxxxx>
> > Reviewed-by: Thomas Garnier <thgarnie@xxxxxxxxxx>
> > ---
> 
> Looks good, but see few nits below.
> 
> Acked-by: Andrii Nakryiko <andriin@xxxxxx>

Thanks!

> 
> >  tools/lib/bpf/bpf.c      |   6 ++-
> >  tools/lib/bpf/bpf.h      |   1 +
> >  tools/lib/bpf/libbpf.c   | 104 +++++++++++++++++++++++++++++++++++++--
> >  tools/lib/bpf/libbpf.h   |   4 ++
> >  tools/lib/bpf/libbpf.map |   3 ++
> >  5 files changed, 114 insertions(+), 4 deletions(-)
> >
> 
> [...]
> 
> > @@ -5084,6 +5099,8 @@ __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz,
> >                 if (prog->type != BPF_PROG_TYPE_UNSPEC)
> >                         continue;
> >
> > +
> > +
> 
> why these extra lines?

Ah this might have crept in my latest rebase. Will remove these.

> 
> >                 err = libbpf_prog_type_by_name(prog->section_name, &prog_type,
> >                                                &attach_type);
> >                 if (err == -ESRCH)
> > @@ -6160,6 +6177,7 @@ bool bpf_program__is_##NAME(const struct bpf_program *prog)       \
> >  }                                                              \
> >
> >  BPF_PROG_TYPE_FNS(socket_filter, BPF_PROG_TYPE_SOCKET_FILTER);
> > +BPF_PROG_TYPE_FNS(lsm, BPF_PROG_TYPE_LSM);
> >  BPF_PROG_TYPE_FNS(kprobe, BPF_PROG_TYPE_KPROBE);
> >  BPF_PROG_TYPE_FNS(sched_cls, BPF_PROG_TYPE_SCHED_CLS);
> >  BPF_PROG_TYPE_FNS(sched_act, BPF_PROG_TYPE_SCHED_ACT);
> > @@ -6226,6 +6244,8 @@ static struct bpf_link *attach_raw_tp(const struct bpf_sec_def *sec,
> >                                       struct bpf_program *prog);
> >  static struct bpf_link *attach_trace(const struct bpf_sec_def *sec,
> >                                      struct bpf_program *prog);
> > +static struct bpf_link *attach_lsm(const struct bpf_sec_def *sec,
> > +                                  struct bpf_program *prog);
> >
> >  struct bpf_sec_def {
> >         const char *sec;
> > @@ -6272,6 +6292,9 @@ static const struct bpf_sec_def section_defs[] = {
> >         SEC_DEF("freplace/", EXT,
> >                 .is_attach_btf = true,
> >                 .attach_fn = attach_trace),
> > +       SEC_DEF("lsm/", LSM,
> > +               .expected_attach_type = BPF_LSM_MAC,
> 
> curious, will there be non-MAC LSM programs? if yes, how they are
> going to be different and which prefix will we use then?

One can think BPF_LSM_AUDIT programs which will only be used to log
information from the LSM hooks and not enforce a policy. Currently,
one can sort of do that by disabling CONFIG_SECURITY_BPF_ENFORCE but
that's an all or none hammer.

> 
> > +               .attach_fn = attach_lsm),
> >         BPF_PROG_SEC("xdp",                     BPF_PROG_TYPE_XDP),
> >         BPF_PROG_SEC("perf_event",              BPF_PROG_TYPE_PERF_EVENT),
> >         BPF_PROG_SEC("lwt_in",                  BPF_PROG_TYPE_LWT_IN),
> > @@ -6533,6 +6556,44 @@ static int bpf_object__collect_struct_ops_map_reloc(struct bpf_object *obj,
> >         return -EINVAL;
> >  }
> >
> > +static __s32 find_lsm_hook_idx(struct bpf_program *prog)
> 
> nit: I'd stick to int for return result, we barely ever use __s32 in libbpf.c

Sure. Changed to int.

- KP

> 
> [...]