AVC denied for docker while trying to set labels for tmpfs mounts

[Paul Moore]

On Wed, Jul 21, 2021 at 2:46 PM Sujithra P <sujithrap at gmail.com> wrote:
>
> Hi SELinux Experts,
>
> The following issue is described in the below post as well.
> https://github.com/containers/container-selinux/issues/141
>
> Occasionally running into the following selinux denials for docker
>
> type=AVC msg=audit(1626732057.636:4583): avc:  denied  { associate }
> for  pid=57450 comm="dockerd" name="/" dev="tmpfs" ino=150014
> scontext=system_u:object_r:container_file_t:s0:c263,c914
> tcontext=system_u:object_r:lib_t:s0 tclass=filesystem permissive=0
>
> type=AVC msg=audit(1626812823.170:9434): avc:  denied  { associate }
> for  pid=20027 comm="dockerd" name="/" dev="tmpfs" ino=198147
> scontext=system_u:object_r:container_file_t:s0:c578,c672
> tcontext=system_u:object_r:locale_t:s0 tclass=filesystem permissive=0
>
>
>  level=error msg="Handler for POST
> /v1.40/containers/a3a875e7896384e3bff53b8317e91ed4301a13957f42187eb227f28e09bd877c/start
> returned error: error setting label on mount source
> '/var/lib/kubelet/pods/f7cee5b2-bcd9-4aa1-9d67-c75b677ba2a1/volumes/kubernetes.io~secret/secret':
> failed to set file label on
> /var/lib/kubelet/pods/f7cee5b2-bcd9-4aa1-9d67-c75b677ba2a1/volumes/kubernetes.io~secret/secret:
> permission denied"
>
>
> Docker is not able to set labels for these tmpfs mounts because they
> end up having wrong labels when they are created (sometimes
> "locale_t", sometimes "lib_t" which of course is not the
> default/correct context for tmpfs fs).
> Apparently semodule -R and deleting these tmps files or reboot of the
> node fixes the problem.
> Not sure what is causing the tmpfs mounts to get wrong labels in the
> first place.
>
> Everything seems to be fine to begin with, but as the system keeps
> scheduling pods on the node, this behavior is observed sometimes (not
> consistent always).
>
>
> OS Details:
>
> NAME="CentOS Linux"
> VERSION="8 (Core)"
> ID="centos"
> ID_LIKE="rhel fedora"
> VERSION_ID="8"
> PLATFORM_ID="platform:el8"
> PRETTY_NAME="CentOS Linux 8 (Core)"
>
> Docker Version:
> Client: Docker Engine - Community
> Version: 19.03.13
> API version: 1.40
> Go version: go1.13.15
> Git commit: 4484c46d9d
> Built: Wed Sep 16 17:02:36 2020
> OS/Arch: linux/amd64
> Experimental: false
>
> Kubernetes Version*
> v1.20.8-gke.1500
>
>
> Any help on how to debug this issue  would be greatly appreciated.

This sounds like it might be a problem with CentOS and/or your Docker
install, have you tried talking with the RH/CentOS folks about this
problem?  We focus mostly on upstream issues here and it isn't clear
to me at this moment that this is an upstream issue.

-- 
paul moore
www.paul-moore.com