Permission denied while trying to connect to Docker socket inside container after updating to 4.28.0

[harichards]

Description

I used to be able to use Docker from within a Docker container by mounting the host socket with:

-v /var/run/docker.sock:/var/run/docker.sock

and adding the host group docker with:

--group-add docker

On the host, the group docker has permission to connect to the Docker socket:

$ ll /var/run/docker.sock
srw-rw---- 1 root docker 0 Mar 12 10:51 /var/run/docker.sock=

However, within a Docker container I get the following after updating to 4.28.0:

$ ll /var/run/docker.sock 
srw-rw---- 1 root root 0 Mar 12 14:51 /var/run/docker.sock=

This results in the following error:

permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock: Get "http://%2Fvar%2Frun%2Fdocker.sock/v1.24/version": dial unix /var/run/docker.sock: connect: permission denied

Reproduce

Create a file named Dockerfile with the following content:

FROM ubuntu:23.04

RUN apt-get update \
 && apt-get -y install ca-certificates curl gnupg

RUN curl -fsSL https://download.docker.com/linux/ubuntu/gpg | gpg --dearmor -o /etc/apt/keyrings/docker.gpg \
 && echo "deb [arch=amd64 signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu/ lunar stable" | tee /etc/apt/sources.list.d/docker.list

RUN apt-get update \
 && apt-get -y install docker-ce-cli

RUN groupadd --gid 1001 docker

Build the Docker image:

$ docker build .

Run the Docker image:

$ docker run -it --rm -v /var/run/docker.sock:/var/run/docker.sock --group-add docker -u ubuntu <image>

Run the following command from within the Docker container:

$ docker version

Expected behavior

No response

docker version

Client:
 Cloud integration: v1.0.35+desktop.11
 Version:           25.0.3
 API version:       1.44
 Go version:        go1.21.6
 Git commit:        4debf41
 Built:             Tue Feb  6 21:13:00 2024
 OS/Arch:           linux/amd64
 Context:           default

Server: Docker Desktop
 Engine:
  Version:          25.0.3
  API version:      1.44 (minimum version 1.24)
  Go version:       go1.21.6
  Git commit:       f417435
  Built:            Tue Feb  6 21:14:25 2024
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.6.28
  GitCommit:        ae07eda36dd25f8a1b98dfbf587313b99c0190bb
 runc:
  Version:          1.1.12
  GitCommit:        v1.1.12-0-g51d5e94
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

docker info

Client:
 Version:    25.0.3
 Context:    default
 Debug Mode: false
 Plugins:
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.12.1-desktop.4
    Path:     /usr/local/lib/docker/cli-plugins/docker-buildx
  compose: Docker Compose (Docker Inc.)
    Version:  v2.24.6-desktop.1
    Path:     /usr/local/lib/docker/cli-plugins/docker-compose
  debug: Get a shell into any image or container. (Docker Inc.)
    Version:  0.0.24
    Path:     /usr/local/lib/docker/cli-plugins/docker-debug
  dev: Docker Dev Environments (Docker Inc.)
    Version:  v0.1.0
    Path:     /usr/local/lib/docker/cli-plugins/docker-dev
  extension: Manages Docker extensions (Docker Inc.)
    Version:  v0.2.22
    Path:     /usr/local/lib/docker/cli-plugins/docker-extension
  feedback: Provide feedback, right in your terminal! (Docker Inc.)
    Version:  v1.0.4
    Path:     /usr/local/lib/docker/cli-plugins/docker-feedback
  init: Creates Docker-related starter files for your project (Docker Inc.)
    Version:  v1.0.1
    Path:     /usr/local/lib/docker/cli-plugins/docker-init
  sbom: View the packaged-based Software Bill Of Materials (SBOM) for an image (Anchore Inc.)
    Version:  0.6.0
    Path:     /usr/local/lib/docker/cli-plugins/docker-sbom
  scout: Docker Scout (Docker Inc.)
    Version:  v1.5.0
    Path:     /usr/local/lib/docker/cli-plugins/docker-scout
WARNING: Plugin "/usr/local/lib/docker/cli-plugins/docker-scan" is not valid: failed to fetch metadata: fork/exec /usr/local/lib/docker/cli-plugins/docker-scan: no such file or directory

Server:
 Containers: 21
  Running: 6
  Paused: 0
  Stopped: 15
 Images: 15
 Server Version: 25.0.3
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 1
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: ae07eda36dd25f8a1b98dfbf587313b99c0190bb
 runc version: v1.1.12-0-g51d5e94
 init version: de40ad0
 Security Options:
  seccomp
   Profile: unconfined
 Kernel Version: 5.15.146.1-microsoft-standard-WSL2
 Operating System: Docker Desktop
 OSType: linux
 Architecture: x86_64
 CPUs: 16
 Total Memory: 15.46GiB
 Name: docker-desktop
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 HTTP Proxy: http.docker.internal:3128
 HTTPS Proxy: http.docker.internal:3128
 No Proxy: hubproxy.docker.internal
 Experimental: false
 Insecure Registries:
  hubproxy.docker.internal:5555
  127.0.0.0/8
 Live Restore Enabled: false

WARNING: No blkio throttle.read_bps_device support
WARNING: No blkio throttle.write_bps_device support
WARNING: No blkio throttle.read_iops_device support
WARNING: No blkio throttle.write_iops_device support
WARNING: daemon is not using the default seccomp profile

Diagnostics ID

n/a

Additional Info

No response

[garylavayou]

I have the same problem with version 4.28.0 (139021) that the mounted /var/run/docker.sock has wrong group name root instead of docker. Also, I tried to change the file permission to rw-rw-rw-, but it still results in rw-rw---- in the container.

Below is the simple test result:

Test on Docker Desktop Windows (WSL2 backend)

$ docker run --rm -it -v /var/run/docker.sock:/var/run/docker.sock ubuntu:jammy /bin/bash
# ls -lh /var/run/docker.sock 
# srw-rw---- 1 root root 0 Mar 17 11:10 /var/run/docker.sock  <- group is root 
$ ls -lh /var/run/docker.sock
# srw-rw---- 1 root docker 0 Mar 17 19:11 /var/run/docker.sock
$ cat /etc/group | grep docker
# docker:x:1001:gary,coder

Output of docker info:

Server:
 Containers: 17
  Running: 5
  Paused: 0
  Stopped: 12
 Images: 58
 Server Version: 25.0.3
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 1
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 nvidia runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: ae07eda36dd25f8a1b98dfbf587313b99c0190bb
 runc version: v1.1.12-0-g51d5e94
 init version: de40ad0
 Security Options:
  seccomp
   Profile: unconfined
 Kernel Version: 5.15.146.1-microsoft-standard-WSL2
 Operating System: Docker Desktop
 OSType: linux
 Architecture: x86_64
 CPUs: 12
 Total Memory: 15.59GiB
 Name: docker-desktop
 ID: e82f575f-b7cd-4036-88f7-7b39898923c8
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 HTTP Proxy: http.docker.internal:3128
 HTTPS Proxy: http.docker.internal:3128
 No Proxy: hubproxy.docker.internal
 Experimental: false
 Insecure Registries:
  hubproxy.docker.internal:5555
  192.168.0.100:5000
  192.168.0.206:32000
  127.0.0.0/8
 Live Restore Enabled: false

For comparison purpose, I also perform the same test on a Linux virtual machine with the generic docker.

Test on Docker Linux (VMWare virtual machine)

$ docker run --rm -it -v /var/run/docker.sock:/var/run/docker.sock ubuntu:jammy /bin/bash
# ls -lh /var/run/docker.sock
# srw-rw---- 1 root 1001 0 Mar 17 01:44 /var/run/docker.sock  <- group is 1001 (docker in host) 
$ ls -lh /var/run/docker.sock
# srw-rw---- 1 root docker 0 Mar 17 09:44 /var/run/docker.sock
$ cat /etc/group | grep docker
# docker:x:1001:gary,coder

Output of docker info:

Server:
 Containers: 4
  Running: 3
  Paused: 0
  Stopped: 1
 Images: 6
 Server Version: 24.0.5
 Storage Driver: overlay2
  Backing Filesystem: extfs
  Supports d_type: true
  Using metacopy: false
  Native Overlay Diff: true
  userxattr: false
 Logging Driver: json-file
 Cgroup Driver: systemd
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
 Swarm: inactive
 Runtimes: io.containerd.runc.v2 runc
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 3dce8eb055cbb6872793272b4f20ed16117344f8
 runc version:
 init version: de40ad0
 Security Options:
  apparmor
  seccomp
   Profile: builtin
  cgroupns
 Kernel Version: 5.15.0-100-generic
 Operating System: Ubuntu Core 22
 OSType: linux
 Architecture: x86_64
 CPUs: 8
 Total Memory: 15.54GiB
 Name: ubuntu-server
 ID: 27db9eb6-45b1-4618-9c5f-b7a3f808ec19
 Docker Root Dir: /var/snap/docker/common/var-lib-docker
 Debug Mode: false
 Experimental: false
 Insecure Registries:
  127.0.0.0/8
 Live Restore Enabled: false

[dcrouch79]

Same problem here, temp fix is to reset the ownership inside the container:

sudo chown root:docker /var/run/docker.sock

(This assumes the container has the docker group definition as the host machine)

Unfortunately, if the docker host is restarted the fix needs to be re-applied.

[garylavayou]

Recent updates of Docker Desktop that related to mounting docker.sock is Docker socket mount restrictions for Enhanced Container Isolation that is a business feature. Docker socket mount restrictions will limit containers from accessing docker engine via the mounted /var/run/docker.sock.

Docker Desktop release notes

4.29.0

• Docker socket mount restrictions with ECI is now generally available.

4.28.0

• Added support for Enhanced Container Isolation Docker socket mount permission on WSL user distros.

4.27.2

• Fixed an issue with the engine socket permissions when mounted inside containers. Fixes docker/for-win#13898

4.27.0

• Organization admins can now configure Docker socket mount permissions when ECI is enabled.

I suspect if the business feature's code base also influences the free Personal tier, where this feature is not enabled at all.

[codeart1st]

I come from 4.27.2 - everything works fine. Upgraded to 4.29.0. Now it's broken for me.

[garylavayou]

After upgrading to 4.30.0 (149282), the problem is resolved.