Use perf inside a docker container without --privileged

Question

I am trying to use the perf tool inside a Docker container to record a given command.

kernel.perf_event_paranoid is set to 1, but the container behaves just as if it were 2, when I don't put the --privileged flag.

I could use --privileged, but the code I am running perf on is not trusted and if I am OK with taking a slight security risk by allowing perf tool, giving privileged rights on the container seems a different level of risk.

Is there any other way to use perf inside the container?

~$ docker version
Client:
 Version:      17.03.1-ce
 API version:  1.27
 Go version:   go1.7.5
 Git commit:   7392c3b/17.03.1-ce
 Built:        Tue May 30 17:59:44 2017
 OS/Arch:      linux/amd64

Server:
 Version:      17.03.1-ce
 API version:  1.27 (minimum version 1.12)
 Go version:   go1.7.5
 Git commit:   7392c3b/17.03.1-ce
 Built:        Tue May 30 17:59:44 2017
 OS/Arch:      linux/amd64
 Experimental: false

~$ cat /proc/sys/kernel/perf_event_paranoid
1
~$ perf record ./my-executable
perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error 1 (Operation not permitted)
perf_event_open(..., 0) failed unexpectedly with error 1 (Operation not permitted)
Error:
You may not have permission to collect stats.
Consider tweaking /proc/sys/kernel/perf_event_paranoid:
 -1 - Not paranoid at all
  0 - Disallow raw tracepoint access for unpriv
  1 - Disallow cpu events for unpriv
  2 - Disallow kernel profiling for unpriv

score 22 · Accepted Answer · edited Jun 30 '17 at 03:15

After some research, the problem is not with the perf_event_paranoid, but with the fact that perf_event_open (syscall) has been blacklisted in docker: https://docs.docker.com/engine/security/seccomp/ "Docker v17.06: Seccomp security profiles for Docker"

Significant syscalls blocked by the default profile

perf_event_open Tracing/profiling syscall, which could leak a lot of information on the host.

My first work-around for this is to have a script that downloads the official seccomp file https://github.com/moby/moby/blob/master/profiles/seccomp/default.json, and adds perf_event_open to the list of white-listed syscalls.

I then start docker with --security-opt seccomp=my-seccomp.json

Can I update this somehow in a running container? Or atleast inject it through docker-compose? — Rajeev Ranjan, Apr 26 '19 at 06:38

score 0 · Answer 2 · answered May 09 '19 at 09:21

0

Run docker with --cap-add SYS_ADMIN

answered May 09 '19 at 09:21

lahjaton_j

727
5
13

2

Doesn't `CAP_SYS_ADMIN` allow a *lot* of other privileges? https://lwn.net/Articles/486306/ Does that make it possible for code inside docker to take over the host kernel by loading modules? – Peter Cordes May 09 '19 at 10:31

Use perf inside a docker container without --privileged

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