[Bug 2133876] Re: chroot can not be killed when invoked as coproc

[Julian Andres Klode]

** Changed in: rust-coreutils (Ubuntu Questing)
       Status: New => Won't Fix

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Title:
  chroot can not be killed when invoked as coproc

Status in rust-coreutils package in Ubuntu:
  Triaged
Status in rust-coreutils source package in Questing:
  Won't Fix
Status in rust-coreutils source package in Resolute:
  Triaged

Bug description:
  In questing and resolute I am unable to kill a bash coprocesses that
  has been invoked with chroot. See details below.

  Because questing replaced chroot from coreutils with chroot from rust-
  coreutils and this behaviour starts with questing I suspect that this
  is a bug in the rust implementation.

  # Steps to reproduce

  $ lxc launch ubuntu-daily:resolute resolute
  $ lxc shell resolute
  $ chroot / /usr/bin/bash -c 'while true; do echo "Hello"; sleep 10; done' &
  [1] 794
  $ ps --forest
  PID TTY          TIME CMD
  758 pts/1    00:00:00 su
  782 pts/1    00:00:00  \_ bash
  794 pts/1    00:00:00      \_ chroot
  795 pts/1    00:00:00      |   \_ bash
  796 pts/1    00:00:00      |       \_ sleep
  797 pts/1    00:00:00      \_ ps
  $ kill 794
  $ ps --forest
  PID TTY          TIME CMD
  795 pts/1    00:00:00 bash
  804 pts/1    00:00:00  \_ sleep
  758 pts/1    00:00:00 su
  782 pts/1    00:00:00  \_ bash
  805 pts/1    00:00:00      \_ ps

  Note that the subprocess invoked by chroot with pid 795 is still
  running. You can also see this because every 10 seconds "Hello" gets
  printed to stdout by the process that is still running.

  You can see the same behaviour on questing.

  # Expected Output

  Let's compare this to the behaviour on noble:
  $ lxc launch ubuntu:noble noble
  $ lxc shell noble
  $ chroot / /usr/bin/bash -c 'while true; do echo "Hello"; sleep 10; done' &
  [1] 1384
  $ ps --forest
  PID TTY          TIME CMD
  559 pts/1    00:00:00 su
  574 pts/1    00:00:00  \_ bash
  1384 pts/1    00:00:00      \_ bash
  1387 pts/1    00:00:00      |   \_ sleep
  1389 pts/1    00:00:00      \_ ps
  $ kill 1384
  $ ps --forest
  PID TTY          TIME CMD
  559 pts/1    00:00:00 su
  574 pts/1    00:00:00  \_ bash
  1396 pts/1    00:00:00      \_ ps

  Note that the process tree after invoking chroot looks different
  compared to questing/resolute and the subprocess invoked by chroot
  actually gets killed.

  # Workaround

  `pkill -P $CHROOT_PID` seems to do what I want. It kills the entire
  process tree of the chroot process.

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