netdev - Re: [PATCH bpf-next] bpf, capabilities: introduce CAP

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Message-ID: <20190829134906.7ecae4e2@gandalf.local.home>
Date:   Thu, 29 Aug 2019 13:49:06 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        James Morris <jmorris@...ei.org>, Jann Horn <jannh@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, kernel-team <kernel-team@...com>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH bpf-next] bpf, capabilities: introduce CAP_BPF

On Thu, 29 Aug 2019 10:23:10 -0700
Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:

> > CAP_TRACE_KERNEL: Use all of perf, ftrace, kprobe, etc.
> > 
> > CAP_TRACE_USER: Use all of perf with scope limited to user mode and uprobes.  
> 
> imo that makes little sense from security pov, since
> such CAP_TRACE_KERNEL (ex kprobe) can trace "unrelated user process"
> just as well. Yet not letting it do cleanly via uprobe.
> Sort of like giving a spare key for back door of the house and
> saying no, you cannot have main door key.

I took it as CAP_TRACE_KERNEL as a superset of CAP_TRACE_USER. That is,
if you have CAP_TRACE_KERNEL, by default you get USER. Where as
CAP_TRACE_USER, is much more limiting.

-- Steve