[Bug 1982555] Re: core dump file empty inside container

[Benjamin Drung]

** Also affects: apport (Ubuntu Bionic)
   Importance: Undecided
       Status: New

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Title:
  core dump file empty inside container

Status in Apport:
  Fix Released
Status in apport package in Ubuntu:
  Fix Released
Status in apport source package in Bionic:
  New
Status in apport source package in Focal:
  Fix Released
Status in apport source package in Jammy:
  Fix Released

Bug description:
  [Impact]

  Apport will write an empty core dump file inside of containers.

  [Test plan]

  Run following testcase script inside a LXC container:

  ```
  rm -f /var/lib/apport/coredump/*
  ulimit -c 1000000
  sleep 86400 &
  killall -3 sleep
  ```

  Apport will write a core dump into /var/lib/apport/coredump, but this
  core dump is empty:

  ```
  $ stat /var/lib/apport/coredump/core._usr_bin_sleep.*
    File: /var/lib/apport/coredump/core._usr_bin_sleep.0.44f483a1-e487-44b3-88d1-805d1026f31d.9059.34839819
    Size: 0         	Blocks: 0          IO Block: 4096   regular empty file
  Device: fd00h/64768d	Inode: 120848663   Links: 1
  Access: (0400/-r--------)  Uid: (    0/    root)   Gid: (    0/    root)
  Access: 2022-07-22 07:54:48.838682067 +0000
  Modify: 2022-07-22 07:54:48.838682067 +0000
  Change: 2022-07-22 07:54:48.838682067 +0000
   Birth: 2022-07-22 07:54:48.838682067 +0000
  ```

  This file should not be empty.

  [Where problems could occur]

  The apport binary is called by the kernel when a process crashes.
  Worst case scenarios include breaking the apport binary and no problem
  report is generated any more (or apport uses too much resources).
  Users will see problems reports inside the container which cause
  additional load or disk usage. The fix is accompanied by a test case.

  [Other Info]

  The autopkgtest for armhf are run inside a LXC container and the test
  case test_core_dump_packaged_sigquit triggers this bug.

  Due to the huge amount of broken autopkgtest tests, the diff for the
  SRUs are bigger than desired. The individual commits in
  https://git.launchpad.net/~ubuntu-core-dev/ubuntu/+source/apport/ are
  probably easier to review.

  * jammy SRU: https://git.launchpad.net/~ubuntu-core-dev/ubuntu/+source/apport/log/?h=1fa042cc27714c407494b3d6dfd0730bb984f3eb
  * focal SRU: https://git.launchpad.net/~ubuntu-core-dev/ubuntu/+source/apport/log/?h=eaa92037c7dfba621719c6f81fd75f6a09e90881

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