From: Steven Rostedt <rostedt@goodmis.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: 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: Tue, 27 Aug 2019 20:44:33 -0400 [thread overview]
Message-ID: <20190827204433.3af91faf@gandalf.local.home> (raw)
In-Reply-To: <CALCETrUOHRMkBRJi_s30CjZdOLDGtdMOEgqfgPf+q0x+Fw7LtQ@mail.gmail.com>
On Tue, 27 Aug 2019 16:34:47 -0700
Andy Lutomirski <luto@kernel.org> wrote:
> > > 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 think that, in principle, CAP_TRACING should allow this, but I'm not
> sure how to achieve that. I suppose we could set up
> inode_operations.permission on tracefs, but what exactly would it do?
> Would it be just like generic_permission() except that it would look
> at CAP_TRACING instead of CAP_DAC_OVERRIDE? That is, you can use
> tracefs if you have CAP_TRACING *or* acl access? Or would it be:
>
> int tracing_permission(struct inode *inode, int mask)
> {
> if (!capable(CAP_TRACING))
> return -EPERM;
>
> return generic_permission(inode, mask);
> }
Perhaps we should make a group for it?
>
> Which would mean that you need ACL *and* CAP_TRACING, so
> administrators would change the mode to 777. That's a bit scary.
>
> And this still doesn't let people even *find* tracefs, since it's
> hidden in debugfs.
>
> So maybe make CAP_TRACING override ACLs but also add /sys/fs/tracing
> and mount tracefs there, too, so that regular users can at least find
> the mountpoint.
I think you missed what I said. It's not hidden in /sys/kernel/debug.
If you enable tracefs, you have /sys/kernel/tracing created, and is
completely separate from debugfs. I only have it *also* automatically
mounted to /sys/kernel/debug/tracing for backward compatibility
reasons, as older versions of trace-cmd will only mount debugfs (as
root), and expect to find it there.
mount -t tracefs nodev /sys/kernel/tracing
-- Steve
>
> >
> > 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.
>
> I think we should.
next prev parent reply other threads:[~2019-08-28 0:44 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 [this message]
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
2019-08-29 17:49 ` Steven Rostedt
2019-08-29 17:19 ` Alexei Starovoitov
2019-08-29 17:47 ` Steven Rostedt
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190827204433.3af91faf@gandalf.local.home \
--to=rostedt@goodmis.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=davem@davemloft.net \
--cc=jannh@google.com \
--cc=jmorris@namei.org \
--cc=keescook@chromium.org \
--cc=kernel-team@fb.com \
--cc=linux-api@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mhiramat@kernel.org \
--cc=netdev@vger.kernel.org \
--cc=peterz@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).