Unable to set/view SELinux labels over NFSv4.2 after upgrading CentOS 7.3=>7.4 (kernel 3.10.0-327 =>3.10.0-693)

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Joined: 2017/11/27 11:05:53

Unable to set/view SELinux labels over NFSv4.2 after upgrading CentOS 7.3=>7.4 (kernel 3.10.0-327 =>3.10.0-693)

Post by ach » 2017/11/28 10:23:14


I'm looking for some guidance on how to troubleshoot/debug an issue with (SELinux) labels over NFS that we've been having as a result of a kernel upgrade CentOS7.3->CentOS7.4 - description below.
I looked around on http://linux-nfs.org and on the NFS-devel mailing list but as this is a direct result of upgrading CentOS I thought I'd check here as well.

So, does anyone know how to get to the bottom of this? Or alternatively where I should go for help instead?
I’d also be interested if anyone has labelled NFSv4.2 working on the latest CentOS kernel.

Thank you very much,

Alexander Hermes


## Summary

In upgrading our servers from CentOS 7.3 to 7.4 we upgraded the kernel from 3.10.0-327.36.2.el7.x86_64 to 3.10.0-693.2.2.el7.x86_64. As a result, NFS v4.2 mounts mounted via /etc/fstab at boot do not have proper SElinux label support - attempting to change labels on a mounted file leads to "Operation Not Supported". `ls -lZ` shows the incorrect labels. Upon rebooting to the earlier kernel version the issue goes away.

## Background

As part of our gitlab HA deployment we use NFS to host data on a back end server that is then mounted by application servers (cf. https://docs.gitlab.com/ce/administrati ... y/nfs.html). To do this we have a fairly typical setup where the server (in this example "enfigitback2-devel") exports a bunch of mounts via /etc/exports which are then mounted on a couple of application servers (“enfigitfront1-devel” / “enfigitfront2-devel”).

## The issue

On the new kernel I am not able to change or view the SELinux labels of files / directories mounted on the client:

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[root@enfigitfront2-devel ~]# chcon --recursive --type ssh_home_t /var/opt/gitlab/.ssh/authorized_keys
chcon: failed to change context of ‘/var/opt/gitlab/.ssh/authorized_keys’ to ‘system_u:object_r:ssh_home_t:s0’: Operation not supported [root@enfigitfront2-devel ~]# uname -r
On the old kernel I am:

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[root@enfigitfront1-devel ~]# chcon --recursive --type ssh_home_t /var/opt/gitlab/.ssh/authorized_keys
[root@enfigitfront1-devel ~]# uname -r

We can't keep using the old kernel forever so I'd like to get to the bottom of this - what could this be due to? How can I debug this further to understand where the "Operation not supported" is coming from?

## Server details
(see also full details for the working client (https://pastebin.com/aw97Dxp9), the non-working one (https://pastebin.com/61uvsz7N) and the server (https://pastebin.com/mCMCfAEx ))

Distro: CentOS 7.4
Kernel (`uname -r`):
* 3.10.0-693.5.2.el7 (server)
* 3.10.0-693.2.2.el7.x86_64 (client - new)
* 3.10.0-327.36.2.el7.x86_64 (client - old)
nfs-utils: RPM package version 1.3.0

Server mount option example:

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Client mount options (/etc/fstab):

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enfigitback2-devel.datcon.co.uk:/export/.ssh    /var/opt/gitlab/.ssh    nfs     defaults,soft,v4.2,rsize=1048576,wsize=1048576,noatime,_netdev,lookupcache=none 0       0
## Debugging I've done

### Mounting by hand
I tried to mount one of the exported mounts "by hand" using `mount` and found the following:
* mounting the same export on a different mount point using the same options as in /etc/fstab yields a mount that has the same issue
* mounting with `nosharecache` results in a mount that *does not* have the issue.
So this suggests some issues related to the cache.

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