PID namespace check seems to no longer be valid

[pmarkowsky]

Running on an Ubuntu 22 VM with a 5.15 kernel the PID namespace check incorrectly identified that it was in a namespace.

This looks like the check for the device number being greater than 4 is outdated.

Debugging Information

user@claus:~/src/amicontained$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 22.04.1 LTS
Release:	22.04
Codename:	jammy

user@claus:~/src/amicontained$ uname -a
Linux claus 5.15.0-46-generic #49-Ubuntu SMP Thu Aug 4 18:03:25 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

user@claus:~/src/amicontained$ ./amicontained -d
Container Runtime: not-found
Has Namespaces:
	pid: true.     <--- Unexpected
	user: false
//Snipped

user@claus:~/src/amicontained$ stat /proc/1/ns
  File: /proc/1/ns
  Size: 0         	Blocks: 0          IO Block: 1024   directory
Device: 17h/23d	Inode: 28440       Links: 2
Access: (0511/dr-x--x--x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2023-04-05 02:33:18.504000164 +0000
Modify: 2023-04-05 02:33:18.504000164 +0000
Change: 2023-04-05 02:33:18.504000164 +0000
 Birth: -

[pmarkowsky]

Pro-tip: don't file bugs when tired.

This looks like the check needs to be updated to follow the symlink in /proc/1/ns/pid to still be valid for the device number.

e.g.

user@claus:~/src/amicontained$ sudo stat -c '%d' /proc/1/ns/pid
23
user@claus:~/src/amicontained$ sudo stat -L -c '%d' /proc/1/ns/pid
4

[Hutch53]

localhost@LAN: /src/amicontained$ sudo stat -c '%d' /proc/1/ns/pid
23
$motocare@Admin:/src/amicontained$ sudo stat -L -c '%d' /proc/1/ns/pid
4