Launching runc through Python blocks shell input if "terminal" is set to true

[marmeladema]

Hello everyone and thank you for the great work 👍

I tried to start a very simple container through a Python script, and it happens that after runc exits, the shell input is "blocked" or "hidden":

• With bash (version 5.0), you can type things, but it will not appear on the screen and you have to type "reset" + enter to reset the terminal and then be able to see what you are typing again
• With sh, it just blocks the terminal in __GI___libc_read (fd=0, buf=0x55c6697d1ac0, nbytes=8192) call and you have to kill it

To setup the container, i just created a /tmp/roots directory, mount binded my / into it and used this configuration file generated from runc spec after having removed the mounts part:

{
	"ociVersion": "1.0.1-dev",
	"process": {
		"terminal": true,
		"user": {
			"uid": 0,
			"gid": 0
		},
		"args": [
			"sleep",
			"2"
		],
		"env": [
			"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
			"TERM=xterm"
		],
		"cwd": "/",
		"capabilities": {
			"bounding": [
				"CAP_AUDIT_WRITE",
				"CAP_KILL",
				"CAP_NET_BIND_SERVICE"
			],
			"effective": [
				"CAP_AUDIT_WRITE",
				"CAP_KILL",
				"CAP_NET_BIND_SERVICE"
			],
			"inheritable": [
				"CAP_AUDIT_WRITE",
				"CAP_KILL",
				"CAP_NET_BIND_SERVICE"
			],
			"permitted": [
				"CAP_AUDIT_WRITE",
				"CAP_KILL",
				"CAP_NET_BIND_SERVICE"
			],
			"ambient": [
				"CAP_AUDIT_WRITE",
				"CAP_KILL",
				"CAP_NET_BIND_SERVICE"
			]
		},
		"rlimits": [
			{
				"type": "RLIMIT_NOFILE",
				"hard": 1024,
				"soft": 1024
			}
		],
		"noNewPrivileges": true
	},
	"root": {
		"path": "rootfs",
		"readonly": true
	},
	"hostname": "runc",
	"linux": {
		"resources": {
			"devices": [
				{
					"allow": false,
					"access": "rwm"
				}
			]
		},
		"namespaces": [
			{
				"type": "pid"
			},
			{
				"type": "network"
			},
			{
				"type": "ipc"
			},
			{
				"type": "uts"
			},
			{
				"type": "mount"
			}
		],
		"maskedPaths": [
			"/proc/kcore",
			"/proc/latency_stats",
			"/proc/timer_list",
			"/proc/timer_stats",
			"/proc/sched_debug",
			"/sys/firmware",
			"/proc/scsi"
		],
		"readonlyPaths": [
			"/proc/asound",
			"/proc/bus",
			"/proc/fs",
			"/proc/irq",
			"/proc/sys",
			"/proc/sysrq-trigger"
		]
	}
}

The Python script is very simple:

import subprocess
import atexit
import time

ARGS = ['runc', 'run', 'myrunc']
print(ARGS)
PROCESS = subprocess.Popen(ARGS)
print('Started subprocess with pid {}'.format(PROCESS.pid))
time.sleep(2)
atexit.register(PROCESS.terminate)

Looking at other issues, i found that it might be related to #1721 because if i set terminal to false, it works fine.

I am using runc 1.0-rc6 on kernel 4.20.0