[PATCH v6 6/13] bpf: add BPF token support to BPF_PROG_LOAD command

[Andrii Nakryiko]

On Tue, Oct 10, 2023 at 6:17 PM Paul Moore <paul at paul-moore.com> wrote:
>
> On Sep 27, 2023 Andrii Nakryiko <andrii at kernel.org> wrote:
> >
> > Add basic support of BPF token to BPF_PROG_LOAD. Wire through a set of
> > allowed BPF program types and attach types, derived from BPF FS at BPF
> > token creation time. Then make sure we perform bpf_token_capable()
> > checks everywhere where it's relevant.
> >
> > Signed-off-by: Andrii Nakryiko <andrii at kernel.org>
> > ---
> >  include/linux/bpf.h                           |  6 ++
> >  include/uapi/linux/bpf.h                      |  2 +
> >  kernel/bpf/core.c                             |  1 +
> >  kernel/bpf/inode.c                            |  6 +-
> >  kernel/bpf/syscall.c                          | 87 ++++++++++++++-----
> >  kernel/bpf/token.c                            | 25 ++++++
> >  tools/include/uapi/linux/bpf.h                |  2 +
> >  .../selftests/bpf/prog_tests/libbpf_probes.c  |  2 +
> >  .../selftests/bpf/prog_tests/libbpf_str.c     |  3 +
> >  9 files changed, 108 insertions(+), 26 deletions(-)
>
> ...
>
> > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
> > index 5c5c2b6648b2..d0b219f09bcc 100644
> > --- a/kernel/bpf/syscall.c
> > +++ b/kernel/bpf/syscall.c
> > @@ -2685,6 +2718,10 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
> >       prog->aux->sleepable = attr->prog_flags & BPF_F_SLEEPABLE;
> >       prog->aux->xdp_has_frags = attr->prog_flags & BPF_F_XDP_HAS_FRAGS;
> >
> > +     /* move token into prog->aux, reuse taken refcnt */
> > +     prog->aux->token = token;
> > +     token = NULL;
> > +
> >       err = security_bpf_prog_alloc(prog->aux);
> >       if (err)
> >               goto free_prog;
>
> As we discussed in the earlier thread, let's tweak/rename/move the
> security_bpf_prog_alloc() call down to just before the bpf_check() call
> so it looks something like this:
>
>   err = security_bpf_prog_load(prog, &attr, token);
>   if (err)
>     goto proper_jump_label;
>
>   err = bpf_check(...);
>
> With the idea being that LSMs which implement the token hooks would
> skip any BPF_PROG_LOAD access controls in security_bpf() and instead
> implement them in security_bpf_prog_load().
>
> We should also do something similar for map_create() and
> security_bpf_map_alloc() in patch 4/13.

Sounds good, will do!


>
> --
> paul-moore.com