runc 1.4 breaks the rule that cmd.Start is called only once that's why process Wait can return an error.

[everzakov]

Description

In startWithCgroupFD function the cmd.Start is called twice (if the first one was unsuccessful). However it breaks the rule that:

// A Cmd cannot be reused after calling its [Cmd.Start], [Cmd.Run],
// [Cmd.Output], or [Cmd.CombinedOutput] methods.

If this rule is broken then Cmd.Wait can return an error because c.goroutine save funcs from the first try but their pipes are closed.

A common example can found in golang/go#76746 (comment)

Steps to reproduce the issue

1. Use Ubuntu 20.04
2. Use cgroups v2
3. Use latest golang version (go version go1.25.5 linux/amd64)

Describe the results you received and expected

Received

vboxuser@vboxuser:~/runc$ sudo make GO=/usr/local/go/bin/go localunittest TESTFLAGS="-run=TestEnter"

....

=== RUN   TestEnter
    exec_test.go:216: unexpected error: read |0: file already closed
--- FAIL: TestEnter (0.33s)
FAIL
FAIL	github.com/opencontainers/runc/libcontainer/integration	4.797s

....

make: *** [Makefile:162: localunittest] Error 1

If c.goroutine = nil is set in defer function, then the everything will be ok.
Expected

vboxuser@vboxuser:~/runc$ sudo make GO=/usr/local/go/bin/go localunittest TESTFLAGS="-run=TestEnter"

....

=== RUN   TestEnter
--- PASS: TestEnter (0.25s)
PASS
ok  	github.com/opencontainers/runc/libcontainer/integration	0.313s

....

What version of runc are you using?

main / runc 1.4

Host OS information

vboxuser@vboxuser:~/runc$ cat /etc/os-release 
NAME="Ubuntu"
VERSION="20.04.6 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04.6 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal

Host kernel information

vboxuser@vboxuser:~/runc$ uname -a
Linux vboxuser 5.4.0-216-generic #236-Ubuntu SMP Fri Apr 11 19:53:21 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux

[@kolyshkin: edited for brevity]

[everzakov]

/cc @kolyshkin