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

[Sujithra P <sujithrap@xxxxxxxxx>]

Thanks Ondrej.  Sorry about that, please find the details below.

On Fri, Jul 23, 2021 at 1:31 AM Ondrej Mosnacek <omosnace@xxxxxxxxxx> wrote:
>
> On Thu, Jul 22, 2021 at 9:25 PM Sujithra P <sujithrap@xxxxxxxxx> wrote:
> > Thanks Ondrej.
> >
> > Kernel version:  Linux #2 SMP Fri Apr 23 09:05:57 PDT 2021 x86_64
> > x86_64 x86_64 GNU/Linux
>
> Somehow that string doesn't contain the actual version :) uname -r
> should return the right version string (something like
> "4.18.0-305.el8.x86_64").

uname -r
5.4.17-2102.201.3.el8uek.x86_64

>
> > yum list installed | grep selinux
> > container-selinux.noarch
> > 2:2.162.0-1.module+el8.4.0+20195+0a4a4953      @ol8_appstream
> > libselinux.x86_64                                 2.9-5.el8
> >                           @ol8_baseos_latest
> > libselinux-utils.x86_64                           2.9-5.el8
> >                           @ol8_baseos_latest
> > python3-libselinux.x86_64                         2.9-5.el8
> >                           @ol8_baseos_latest
> > rpm-plugin-selinux.x86_64                         4.14.3-13.el8
> >                           @ol8_baseos_latest
> > selinux-policy.noarch                             3.14.3-67.0.1.el8
> >                           @ol8_baseos_latest
> > selinux-policy-targeted.noarch                    3.14.3-67.0.1.el8
> >                           @ol8_baseos_latest
> >
> > No unusual errors/warnings in dmesg except
> >
> > SELinux: mount invalid. Same superblock, different security settings
> > for (dev mqueue, type mqueue)
> >
> > but I believe this is not harmful?
>
> Yes, that should be unrelated and (probably) harmless.
>
> FWIW, I did find a data race bug in the related code, but at this
> point I don't see how it would cause the behavior you're seeing. I
> also haven't been able to reproduce the issue by trying to trigger the
> race condition. So it may be just a red herring or I'm just missing
> some key element that makes it happen. I'll keep digging...
>

Please let me know if any additional info could help?

I could reproduce this issue and can provide any needed debug information.

Thanks.

> > Thanks.
> >
> > On Thu, Jul 22, 2021 at 3:07 AM Ondrej Mosnacek <omosnace@xxxxxxxxxx> wrote:
> > >
> > > On Thu, Jul 22, 2021 at 12:23 AM Sujithra P <sujithrap@xxxxxxxxx> 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
> > > > always consistent).
> > > >
> > > >
> > > > 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 looks really weird. Could be some subtle kernel bug. What is your
> > > kernel version (run `uname -r`)? Are there any unusual errors/warnings
> > > in the kernel log (`dmesg`) when this happens?
> > >
> > > --
> > > Ondrej Mosnacek
> > > Software Engineer, Linux Security - SELinux kernel
> > > Red Hat, Inc.
> > >
> >
>
> --
> Ondrej Mosnacek
> Software Engineer, Linux Security - SELinux kernel
> Red Hat, Inc.
>

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