Docker "start" hangs when attaching stdin to container

General
1

After upgrading to docker 20.10.4 (does not happen with previous versions), the following hangs:

docker create --rm -i --name test busybox pwd
docker start -i test

Does not happen without the “-i” flags.

This is my docker version:

Client: Docker Engine - Community
 Version:           20.10.4
 API version:       1.41
 Go version:        go1.13.15
 Git commit:        d3cb89e
 Built:             Thu Feb 25 07:06:20 2021
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

Server: Docker Engine - Community
 Engine:
  Version:          20.10.4
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.13.15
  Git commit:       363e9a8
  Built:            Thu Feb 25 07:04:45 2021
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.4.3
  GitCommit:        269548fa27e0089a8b8278fc4fc781d7f65a939b
 runc:
  Version:          1.0.0-rc92
  GitCommit:        ff819c7e9184c13b7c2607fe6c30ae19403a7aff
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0
2

It seems the cause has already been found and corrected: