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[release/1.7] Update AppArmor template to allow confined runc to kill containers #10129

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k8s-infra-cherrypick-robot

This is an automated cherry-pick of #10123

/assign samuelkarp

/usr/sbin/runc is confined with "runc" profile[1] introduced in AppArmor
v4.0.0. This change breaks stopping of containers, because the profile
assigned to containers doesn't accept signals from the "runc" peer.
AppArmor >= v4.0.0 is currently part of Ubuntu Mantic (23.10) and later.

The issue is reproducible both with nerdctl and ctr clients. In the case
of ctr, the --apparmor-default-profile flag has to be specified,
otherwise the container processes would inherit the runc profile, which
behaves as unconfined, and so the subsequent runc process invoked to
stop it would be able to signal it.

  Test commands:

    root@cloudimg:~# nerdctl run -d --name foo nginx:latest
    3d1e74bfe6e7b2912d9223050ae8a81a8f4b73de0846e6d9c956c1e411cdd95a
    root@cloudimg:~# nerdctl stop foo
    FATA[0000] 1 errors:
    unknown error after kill: runc did not terminate successfully: exit status 1: unable to signal init: permission denied
    : unknown

    or

    root@cloudimg:~# ctr pull docker.io/library/nginx:latest
    ...
    root@cloudimg:~# ctr run -d --apparmor-default-profile ctr-default docker.io/library/nginx:latest foo
    root@cloudimg:~# ctr task kill foo
    ctr: unknown error after kill: runc did not terminate successfully: exit status 1: unable to signal init: permission denied
    : unknown

  Relevant syslog messages (with long lines wrapped):

    Apr 23 22:03:12 cloudimg kernel: audit:
      type=1400 audit(1713909792.064:262): apparmor="DENIED"
      operation="signal" class="signal" profile="nerdctl-default"
      pid=13483 comm="runc" requested_mask="receive"
      denied_mask="receive" signal=quit peer="runc"

    or

    Apr 23 22:05:32 cloudimg kernel: audit:
      type=1400 audit(1713909932.106:263): apparmor="DENIED"
      operation="signal" class="signal" profile="ctr-default"
      pid=13574 comm="runc" requested_mask="receive"
      denied_mask="receive" signal=quit peer="runc"

This change extends the default profile with rules that allow receiving
signals from processes that run confined with either runc or crun
profile (crun[2] is an alternative OCI runtime that's also confined in
AppArmor >= v4.0.0, see [1]). It is backward compatible because the peer
value is a regular expression (AARE) so the referenced profile doesn't
have to exist for this profile to successfully compile and load.

[1] https://gitlab.com/apparmor/apparmor/-/commit/2594d936
[2] https://github.com/containers/crun

Signed-off-by: Tomáš Virtus <nechtom@gmail.com>
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Hi @k8s-infra-cherrypick-robot. Thanks for your PR.

I'm waiting for a containerd member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

@dmcgowan dmcgowan changed the title [release/1.7] apparmor: Allow confined runc to kill containers [release/1.7] Update AppArmor template to allow confined runc to kill containers Apr 24, 2024
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spiderman pointing to spiderman meme, showing k8s-infra-cherrypick-robot and k8s-ci-robot as spiderman

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/ok-to-test

@samuelkarp samuelkarp merged commit fb2d43a into containerd:release/1.7 Apr 25, 2024
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6 participants