Comment 0 for bug 1390592

I was helping a docker user out in #apparmor on OFTC and I think we found a kernel bug. Filing this on behalf of the user.

The user added the following to the base abstraction then reloaded policy:
  ptrace peer=@{profile_name},

but had denials like this:
  apparmor="DENIED" operation="ptrace" profile="docker-default" pid=15426 comm="ps" requested_mask="trace" denied_mask="trace" peer="docker-default"

The user tried this rule too, but it didn't work:
  ptrace peer=docker-default,

The user had to use 'ptrace,' instead to make the denials go away.

Steps to reproduce:
1. adjust /etc/apparmor.d/abstractions/base to have:
  ptrace peer=@{profile_name},
2. sudo apt-get install docker.io
3. sudo docker pull ubuntu:trusty
4. Run 'ps' inside docker:
   $ sudo docker run -i -t ubuntu:trusty bash
   root@5039d725a41d:/# ps
   ...
   root@5039d725a41d:/# exit
   $

Then observe the following denials on the host:
Nov 7 13:43:42 sec-trusty-amd64 kernel: [24258.018580] type=1400 audit(1415389422.303:68): apparmor="DENIED" operation="ptrace" profile="docker-default" pid=27542 comm="ps" requested_mask="trace" denied_mask="trace" peer="docker-default"
Nov 7 13:43:42 sec-trusty-amd64 kernel: [24258.020832] type=1400 audit(1415389422.307:69): apparmor="DENIED" operation="ptrace" profile="docker-default" pid=27542 comm="ps" requested_mask="read" denied_mask="read" peer="docker-default"
Nov 7 13:43:42 sec-trusty-amd64 kernel: [24258.020893] type=1400 audit(1415389422.307:70): apparmor="DENIED" operation="ptrace" profile="docker-default" pid=27542 comm="ps" requested_mask="read" denied_mask="read" peer="docker-default"

Note, docker is different than most applications in that it embeds its policy inside the docker binary and this binary when launched as a daemon (ie, via the upstart job) will unconditionally write out the policy to /etc/apparmor.d/docker-default. As such, to modify the policy:

0. install docker.io and pull a trusty image # only has to be done once
1. update /etc/apparmor.d/abstractions/base to have the new ptrace rules
2. sudo stop docker.io
3. sudo apparmor_parser -R /etc/apparmor.d/docker
4. sudo rm -f /etc/apparmor.d/docker /etc/apparmor.d/cache/docker
5. sudo start docker.io
6. Run 'ps' inside docker:
   $ sudo docker run -i -t ubuntu:trusty bash
   root@5039d725a41d:/# ps
   ...
   root@5039d725a41d:/# exit
   $

(Docker just added a way to specify an alternate existing profile in https://docs.docker.com/reference/run/#security-configuration).

Reference: https://github.com/docker/docker/issues/7276