From: Andy Lutomirski <luto@kernel.org>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Andy Lutomirski <luto@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Peter Zijlstra <peterz@infradead.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>,
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: Thu, 29 Aug 2019 10:36:39 -0700 [thread overview]
Message-ID: <CALCETrUJt9YgV_q2EuqS0-u0HzLrTopkMkvO+NC05C13xUnDxw@mail.gmail.com> (raw)
In-Reply-To: <20190829172309.xd73ax4wgsjmv6zg@ast-mbp.dhcp.thefacebook.com>
On Thu, Aug 29, 2019 at 10:23 AM Alexei Starovoitov
<alexei.starovoitov@gmail.com> wrote:
>
> On Thu, Aug 29, 2019 at 08:43:23AM -0700, Andy Lutomirski wrote:
> >
> > I can imagine splitting it into three capabilities:
> >
> > CAP_TRACE_KERNEL: learn which kernel functions are called when. This
> > would allow perf profiling, for example, but not sampling of kernel
> > regs.
> >
> > CAP_TRACE_READ_KERNEL_DATA: allow the tracing, profiling, etc features
> > that can read the kernel's data. So you get function arguments via
> > kprobe, kernel regs, and APIs that expose probe_kernel_read()
> >
> > CAP_TRACE_USER: trace unrelated user processes
> >
> > I'm not sure the code is written in a way that makes splitting
> > CAP_TRACE_KERNEL and CAP_TRACE_READ_KERNEL_DATA, and I'm not sure that
> > CAP_TRACE_KERNEL is all that useful except for plain perf record
> > without CAP_TRACE_READ_KERNEL_DATA. What do you all think? I suppose
> > it could also be:
> >
> > CAP_PROFILE_KERNEL: Use perf with events that aren't kprobes or
> > tracepoints. Does not grant the ability to sample regs or the kernel
> > stack directly.
> >
> > 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.
>
Not all combinations of capabilities make total sense. CAP_SETUID,
for example, generally lets you get all the other capabilities.
CAP_TRACE_KERNEL + CAP_TRACE_USER makes sense. CAP_TRACE_USER by
itself makes sense. CAP_TRACE_READ_KERNEL_DATA without
CAP_TRACE_KERNEL does not. I don't think this is a really a problem.
next prev parent reply other threads:[~2019-08-29 17:36 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
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 [this message]
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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