From: Masami Hiramatsu <mhiramat@kernel.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Kees Cook <keescook@chromium.org>,
LSM List <linux-security-module@vger.kernel.org>,
James Morris <jmorris@namei.org>, Jann Horn <jannh@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Masami Hiramatsu <mhiramat@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
Daniel Borkmann <daniel@iogearbox.net>,
Network Development <netdev@vger.kernel.org>,
bpf <bpf@vger.kernel.org>, kernel-team <kernel-team@fb.com>,
Linux API <linux-api@vger.kernel.org>
Subject: Re: [PATCH bpf-next] bpf, capabilities: introduce CAP_BPF
Date: Wed, 28 Aug 2019 12:30:41 +0900 [thread overview]
Message-ID: <20190828123041.c0c90c15865897461ee819a2@kernel.org> (raw)
In-Reply-To: <20190827192144.3b38b25a@gandalf.local.home>
On Tue, 27 Aug 2019 19:21:44 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:
> > Here's my proposal for CAP_TRACING, documentation-style:
> >
> > --- begin ---
> >
> > CAP_TRACING enables a task to use various kernel features to trace
> > running user programs and the kernel itself. CAP_TRACING also enables
> > a task to bypass some speculation attack countermeasures. A task in
> > the init user namespace with CAP_TRACING will be able to tell exactly
> > what kernel code is executed and when, and will be able to read kernel
> > registers and kernel memory. It will, similarly, be able to read the
> > state of other user tasks.
> >
> > Specifically, CAP_TRACING allows the following operations. It may
> > allow more operations in the future:
> >
> > - Full use of perf_event_open(), similarly to the effect of
> > kernel.perf_event_paranoid == -1.
> >
> > - Loading and attaching tracing BPF programs, including use of BPF
> > raw tracepoints.
> >
> > - Use of BPF stack maps.
> >
> > - Use of bpf_probe_read() and bpf_trace_printk().
> >
> > - Use of unsafe pointer-to-integer conversions in BPF.
> >
> > - Bypassing of BPF's speculation attack hardening measures and
> > constant blinding. (Note: other mechanisms might also allow this.)
> >
> > CAP_TRACING does not override normal permissions on sysfs or debugfs.
> > This means that, unless a new interface for programming kprobes and
> > such is added, it does not directly allow use of kprobes.
>
> 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?
> 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.
Also, there is a blacklist of kprobes under debugfs. If CAP_TRACING
introduced and it allows to access kallsyms, I would like to move the
blacklist under tracefs, or make an alias of blacklist entry on tracefs.
Thank you,
--
Masami Hiramatsu <mhiramat@kernel.org>
next prev parent reply other threads:[~2019-08-28 3:30 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190827205213.456318-1-ast@kernel.org>
2019-08-27 23:01 ` [PATCH bpf-next] bpf, capabilities: introduce CAP_BPF Andy Lutomirski
2019-08-27 23:21 ` Steven Rostedt
2019-08-27 23:34 ` Andy Lutomirski
2019-08-28 0:44 ` Steven Rostedt
2019-08-28 1:12 ` Andy Lutomirski
2019-08-28 2:22 ` Steven Rostedt
2019-08-28 0:38 ` Alexei Starovoitov
2019-08-28 3:30 ` Masami Hiramatsu [this message]
2019-08-28 4:47 ` Alexei Starovoitov
2019-08-28 0:34 ` Alexei Starovoitov
2019-08-28 0:55 ` Andy Lutomirski
2019-08-28 2:00 ` Andy Lutomirski
2019-08-28 4:49 ` Alexei Starovoitov
2019-08-28 6:20 ` Andy Lutomirski
2019-08-28 23:38 ` Alexei Starovoitov
2019-08-29 0:58 ` Andy Lutomirski
2019-08-28 4:43 ` Alexei Starovoitov
2019-08-28 6:12 ` Andy Lutomirski
2019-08-28 22:55 ` Alexei Starovoitov
2019-08-29 0:45 ` Andy Lutomirski
2019-08-29 0:53 ` Andy Lutomirski
2019-08-29 4:07 ` Alexei Starovoitov
2019-09-28 23:37 ` Steven Rostedt
2019-09-30 18:31 ` Kees Cook
2019-10-01 1:22 ` Alexei Starovoitov
2019-10-01 22:10 ` Steven Rostedt
2019-10-01 22:18 ` Alexei Starovoitov
2019-10-01 22:47 ` Steven Rostedt
2019-10-02 17:18 ` Alexei Starovoitov
2019-10-02 23:00 ` Steven Rostedt
2019-10-03 16:18 ` trace_printk issue. Was: " Alexei Starovoitov
2019-10-03 16:41 ` Steven Rostedt
2019-10-04 19:56 ` Alexei Starovoitov
2019-10-03 6:12 ` Masami Hiramatsu
2019-10-03 16:20 ` Alexei Starovoitov
2019-08-28 7:14 ` Peter Zijlstra
2019-08-28 22:08 ` Alexei Starovoitov
2019-08-29 13:34 ` Steven Rostedt
2019-08-29 15:43 ` Andy Lutomirski
2019-08-29 17:23 ` Alexei Starovoitov
2019-08-29 17:36 ` Andy Lutomirski
2019-08-29 17:49 ` Steven Rostedt
2019-08-29 17:19 ` Alexei Starovoitov
2019-08-29 17:47 ` Steven Rostedt
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