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Re: [PATCH 1/6] ebpf: add a seccomp program type

From Kees Cook <keescook@chromium.org>
Newsgroups linux.kernel
Subject Re: [PATCH 1/6] ebpf: add a seccomp program type
Date 2015-09-04 23:10 +0200
Message-ID <q56pc-5eU-25@gated-at.bofh.it> (permalink)
References <q51IS-70a-7@gated-at.bofh.it> <q51IT-70a-29@gated-at.bofh.it> <q55Wb-4s0-21@gated-at.bofh.it> <q56pc-5eU-27@gated-at.bofh.it>
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On Fri, Sep 4, 2015 at 2:06 PM, Tycho Andersen
<tycho.andersen@canonical.com> wrote:
> On Fri, Sep 04, 2015 at 01:34:12PM -0700, Kees Cook wrote:
>> On Fri, Sep 4, 2015 at 9:04 AM, Tycho Andersen
>> <tycho.andersen@canonical.com> wrote:
>> > +static const struct bpf_func_proto *
>> > +seccomp_func_proto(enum bpf_func_id func_id)
>> > +{
>> > +       /* Right now seccomp eBPF loading doesn't support maps; seccomp filters
>> > +        * are considered to be read-only after they're installed, so map fds
>> > +        * probably need to be invalidated when a seccomp filter with maps is
>> > +        * installed.
>> > +        *
>> > +        * The rest of these might be reasonable to call from seccomp, so we
>> > +        * export them.
>> > +        */
>> > +       switch (func_id) {
>> > +       case BPF_FUNC_ktime_get_ns:
>> > +               return &bpf_ktime_get_ns_proto;
>> > +       case BPF_FUNC_trace_printk:
>> > +               return bpf_get_trace_printk_proto();
>> > +       case BPF_FUNC_get_prandom_u32:
>> > +               return &bpf_get_prandom_u32_proto;
>> > +       case BPF_FUNC_get_smp_processor_id:
>> > +               return &bpf_get_smp_processor_id_proto;
>> > +       case BPF_FUNC_tail_call:
>> > +               return &bpf_tail_call_proto;
>> > +       case BPF_FUNC_get_current_pid_tgid:
>> > +               return &bpf_get_current_pid_tgid_proto;
>> > +       case BPF_FUNC_get_current_uid_gid:
>> > +               return &bpf_get_current_uid_gid_proto;
>> > +       case BPF_FUNC_get_current_comm:
>> > +               return &bpf_get_current_comm_proto;
>> > +       default:
>> > +               return NULL;
>> > +       }
>> > +}
>>
>> While this list is probably fine, I don't want to mix the addition of
>> eBPF functions to the seccomp ABI with the CRIU changes. No function
>> calls are currently possible and it should stay that way.
>
> Ok, I can remove them.
>
>> I was expecting to see a validator, similar to the existing BPF
>> validator that is called when creating seccomp filters currently. Can
>> we add a similar validator for new BPF_PROG_TYPE_SECCOMP?
>
> That's effectively what this patch does; when the eBPF is loaded via
> bpf(), you tell bpf() you want a BPF_PROG_TYPE_SECCOMP, and it invokes
> this validation/translation code, i.e. it uses
> seccomp_is_valid_access() to check and make sure access are aligned
> and inside struct seccomp_data.

What about limiting the possible instructions?

-Kees

-- 
Kees Cook
Chrome OS Security
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Thread

c/r of seccomp filters via underlying eBPF Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 18:10 +0200
  [PATCH 5/6] seccomp: add a way to attach a filter via eBPF fd Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 18:10 +0200
    Re: [PATCH 5/6] seccomp: add a way to attach a filter via eBPF fd Kees Cook <keescook@chromium.org> - 2015-09-04 22:50 +0200
      Re: [PATCH 5/6] seccomp: add a way to attach a filter via eBPF fd "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com> - 2015-09-05 09:20 +0200
    Re: [PATCH 5/6] seccomp: add a way to attach a filter via eBPF fd Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-04 22:50 +0200
  [PATCH 4/6] seccomp: add a way to access filters via bpf fds Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 18:10 +0200
    Re: [PATCH 4/6] seccomp: add a way to access filters via bpf fds Kees Cook <keescook@chromium.org> - 2015-09-04 22:30 +0200
      Re: [PATCH 4/6] seccomp: add a way to access filters via bpf fds Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-04 22:40 +0200
        Re: [PATCH 4/6] seccomp: add a way to access filters via bpf fds Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 23:00 +0200
  [PATCH 6/6] ebpf: allow BPF_REG_X in src_reg conditional jumps Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 18:10 +0200
    Re: [PATCH 6/6] ebpf: allow BPF_REG_X in src_reg conditional jumps Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-04 23:10 +0200
      Re: [PATCH 6/6] ebpf: allow BPF_REG_X in src_reg conditional jumps Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-05 00:50 +0200
        Re: [PATCH 6/6] ebpf: allow BPF_REG_X in src_reg conditional jumps Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-05 06:20 +0200
  [PATCH 1/6] ebpf: add a seccomp program type Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 18:10 +0200
    Re: [PATCH 1/6] ebpf: add a seccomp program type Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-04 22:20 +0200
      Re: [PATCH 1/6] ebpf: add a seccomp program type Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 23:10 +0200
    Re: [PATCH 1/6] ebpf: add a seccomp program type Kees Cook <keescook@chromium.org> - 2015-09-04 22:40 +0200
      Re: [PATCH 1/6] ebpf: add a seccomp program type Kees Cook <keescook@chromium.org> - 2015-09-04 23:10 +0200
      Re: [PATCH 1/6] ebpf: add a seccomp program type Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 23:10 +0200
    Re: [PATCH 1/6] ebpf: add a seccomp program type Andy Lutomirski <luto@amacapital.net> - 2015-09-05 00:00 +0200
  [PATCH 3/6] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 18:10 +0200
    Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Kees Cook <keescook@chromium.org> - 2015-09-04 22:20 +0200
      Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 22:50 +0200
        Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-04 23:00 +0200
          Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 23:10 +0200
        Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Kees Cook <keescook@chromium.org> - 2015-09-04 23:00 +0200
        Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Andy Lutomirski <luto@amacapital.net> - 2015-09-04 23:50 +0200
          Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-05 00:30 +0200
            Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Andy Lutomirski <luto@amacapital.net> - 2015-09-05 01:10 +0200
              Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-05 02:30 +0200
            Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Kees Cook <keescook@chromium.org> - 2015-09-05 01:30 +0200
              Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Andy Lutomirski <luto@amacapital.net> - 2015-09-05 02:10 +0200
    Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Alexei Starovoitov <alexei.starovoitov@gmail.com> - 2015-09-04 22:30 +0200
      Re: [PATCH 3/6] ebpf: add a way to dump an eBPF program Tycho Andersen <tycho.andersen@canonical.com> - 2015-09-04 22:50 +0200

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