Unable to execute binary file in Docker container ("Operation not permitted")

Question

Problem

I am building a Docker container (based on RHEL) that includes a custom binary from a third-party repository. When executing the binary in the container, I receive a nondescript error: "Operation not permitted".

Analysis

Dockerfile

The Dockerfile is fairly simple.

FROM dockerregistry.example.com/rhel7:latest

RUN yum -y install \
    curl \
    custom-package && \
    curl -Lsq https://github.com/Yelp/dumb-init/releases/download/v1.2.0/dumb-init_1.2.0_amd64 > /sbin/dumb-init && \
    chmod 755 /sbin/dumb-init && \
    yum clean all

ADD custom-package.conf /etc/custom-package/custom-package.conf

ENTRYPOINT ["/sbin/dumb-init", "--"]
CMD ["/usr/local/custom-package/bin/custom-package", "--config", "/etc/custom-package/custom-package.conf"]

Building the image

I build and enter the container on my workstation using the following commands.

$ docker build -t custom-package:v1 .
$ docker run --security-opt seccomp:unconfined -d custom-package:v1 tail -f /dev/null
$ docker exec -it <image ID> /bin/bash

"Operation not permitted"

Once I'm inside the image, if I try executing the binary, I receive an extremely unhelpful error. Running strace also gives a confusing output. On inspecting file permissions and metadata, it appears to be fine.

# /usr/local/telegraf/bin/telegraf
bash: /usr/local/telegraf/bin/telegraf: Operation not permitted

# strace -f /usr/local/telegraf/bin/telegraf
execve("/usr/local/telegraf/bin/telegraf", ["/usr/local/telegraf/bin/telegraf"], [/* 17 vars */]) = -1 EPERM (Operation not permitted)
write(2, "strace: exec: Operation not perm"..., 38strace: exec: Operation not permitted
) = 38
exit_group(1)                           = ?
+++ exited with 1 +++

# ls -l /usr/local/telegraf/bin/telegraf    
-rwxr-xr-x 1 telegraf telegraf 38664736 Jun  3 15:41 /usr/local/telegraf/bin/telegraf

# getcap -v /usr/local/telegraf/bin/telegraf
/usr/local/telegraf/bin/telegraf = cap_sys_rawio+ep

I am unable to collect enough information to debug my container and why the executable binary isn't working. Is there something that stands out as wrong or a reason why I would receive an unhelpful error like this?

Thanks!

Answer 1

The SYS_RAWIO capability needs the --privileged option to access the devices. See capabilities(7).

http://man7.org/linux/man-pages/man7/capabilities.7.html

   CAP_SYS_RAWIO
          * Perform I/O port operations (iopl(2) and ioperm(2));
          * access /proc/kcore;
          * employ the FIBMAP ioctl(2) operation;
          * open devices for accessing x86 model-specific registers (MSRs, see msr(4))
          * update /proc/sys/vm/mmap_min_addr;
          * create memory mappings at addresses below the value specified by /proc/sys/vm/mmap_min_addr;
          * map files in /proc/bus/pci;
          * open /dev/mem and /dev/kmem;
          * perform various SCSI device commands;
          * perform certain operations on hpsa(4) and cciss(4) devices;
          * perform a range of device-specific operations on other devices.