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

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Message-ID: <20190828044733.vvudyncwq5nffe4l@ast-mbp.dhcp.thefacebook.com>
Date:   Tue, 27 Aug 2019 21:47:34 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        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>,
        "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 Wed, Aug 28, 2019 at 12:30:41PM +0900, Masami Hiramatsu wrote:
> > kprobes can be created in the tracefs filesystem (which is separate from
> > debugfs, tracefs just gets automatically mounted
> > in /sys/kernel/debug/tracing when debugfs is mounted) from the
> > kprobe_events file. /sys/kernel/tracing is just the tracefs
> > directory without debugfs, and was created specifically to allow
> > tracing to be access without opening up the can of worms in debugfs.
> 
> I like the CAP_TRACING for tracefs. Can we make the tracefs itself
> check the CAP_TRACING and call file_ops? or each tracefs file-ops
> handlers must check it?

Thanks for the feedback.
I'll hack a prototype of CAP_TRACING for perf bits that I understand
and you folks will be able to use it in ftrace when initial support lands.
imo the question above is an implementation detail that you can resolve later.
I see it as a followup to initial CAP_TRACING drop.