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

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Message-ID: <20190828003813.fkar6udy5vq4loe5@ast-mbp.dhcp.thefacebook.com>
Date:   Tue, 27 Aug 2019 17:38:14 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Andy Lutomirski <luto@...nel.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>,
        Peter Zijlstra <peterz@...radead.org>,
        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 Tue, Aug 27, 2019 at 07:21:44PM -0400, Steven Rostedt wrote:
> 
> At least for CAP_TRACING (if it were to allow read/write access
> to /sys/kernel/tracing), that would be very useful. It would be useful
> to those that basically own their machines, and want to trace their
> applications all the way into the kernel without having to run as full
> root.

+1

The proposal is to have CAP_TRACING to control perf and ftrace.
perf and trace-cmd binaries could be installed with CAP_TRACING and that's
all they need to do full tracing.

I can craft a patch for perf_event_open side and demo CAP_TRACING.
Once that cap bit is ready you can use it on ftrace side?

> Should we allow CAP_TRACING access to /proc/kallsyms? as it is helpful
> to convert perf and trace-cmd's function pointers into names. Once you
> allow tracing of the kernel, hiding /proc/kallsyms is pretty useless.

yep.