Bug 1558564 - Mounting socket files from subPaths fail
Summary: Mounting socket files from subPaths fail
Alias: None
Product: OpenShift Container Platform
Classification: Red Hat
Component: Storage
Version: 3.9.0
Hardware: Unspecified
OS: Unspecified
Target Milestone: ---
: 3.9.z
Assignee: Hemant Kumar
QA Contact: Qin Ping
Depends On:
Blocks: 1560710 1563317 1563329 1563336
TreeView+ depends on / blocked
Reported: 2018-03-20 13:54 UTC by Hemant Kumar
Modified: 2018-05-17 06:44 UTC (History)
3 users (show)

Fixed In Version:
Doc Type: If docs needed, set a value
Doc Text:
Clone Of:
: 1560710 1563317 1563329 1563336 (view as bug list)
Last Closed: 2018-05-17 06:43:34 UTC
Target Upstream Version:

Attachments (Terms of Use)

System ID Priority Status Summary Last Updated
Red Hat Product Errata RHBA-2018:1566 None None None 2018-05-17 06:44:07 UTC

Description Hemant Kumar 2018-03-20 13:54:26 UTC
Description of problem:

Mounting sockets or special files from subpaths fails.

Version-Release number of selected component (if applicable): 3.9.x

How reproducible:

Steps to Reproduce:
1. Create a pod definition that uses "/" as hostPath.
2. Try and mount something like "/run/docker.sock" as a subpath within a container.
3. The pod will fail to start

The reason of this regression is - openat system call being used on https://github.com/kubernetes/kubernetes/blob/master/pkg/util/mount/mount_linux.go#L1138 does not work for special files like Unix sockets and it will throw - Errno::ENXIO: No such device or address /run/docker.sock

Actual results:

The pod fails to start

Expected results:
The pod should start

Comment 1 Hemant Kumar 2018-03-20 14:34:25 UTC
For now, while we make the fix. One possible workaround is to directly mount "/run/docker.sock" via a new volume entry and a new VolumeMounts entry that does not uses subpath.

Something like:

VolumeMounts: [
{ mountPath: "/run/docker.sock", name: docker_sock, readOnly: true}
volumes: [
{ name: docker_sock,
hostPath: { path: "/run/docker.sock", type: "" },

Comment 2 Hemant Kumar 2018-03-22 20:41:08 UTC
PR upstream for the fix https://github.com/kubernetes/kubernetes/pull/61480

Comment 3 Hemant Kumar 2018-03-26 15:30:50 UTC
Opened PR for Openshift/origin - https://github.com/openshift/origin/pull/19100

Comment 4 Hemant Kumar 2018-04-11 19:12:08 UTC
This is merged in both origin and OSE.So it is done and done from development POV.

Comment 6 Qin Ping 2018-04-17 06:19:58 UTC
Verified in OCP: v3.9.22

# cat pod.yaml 
kind: Pod
apiVersion: v1
  name: testpod
    - name: testpod
      image: aosqe/hello-openshift
        - containerPort: 80
          name: "http-server"
      - mountPath: "/mnt/run/docker.sock"
        subPath: "run/docker.sock"
        name: file
    - name: file
        path: "/"

# oc exec testpod -- ls /mnt/run/docker.sock -l
srw-rw----    1 root     root             0 Apr 17 02:42 /mnt/run/docker.sock

Comment 8 Qin Ping 2018-04-20 02:39:27 UTC
Verified in OCP:
oc v3.9.24
openshift v3.9.24
kubernetes v1.9.1+a0ce1bc657

# uname -a
Linux host-172-16-120-35 3.10.0-693.21.1.el7.x86_64 #1 SMP Fri Feb 23 18:54:16 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

# cat /etc/redhat-release 
Red Hat Enterprise Linux Server release 7.4 (Maipo)

Comment 11 errata-xmlrpc 2018-05-17 06:43:34 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.


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