[Bug 1943982] Re: Revert resolved-disable-event-sources-before-unreffing-them.patch

[Lukas Märdian]

Closing, as agreed upon with the SRU team:
https://code.launchpad.net/~slyon/ubuntu/+source/systemd/+git/systemd/+merge/408816/comments/1079349

** Changed in: systemd (Ubuntu Focal)
       Status: New => Won't Fix

** Changed in: systemd (Ubuntu)
       Status: New => Won't Fix

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Title:
  Revert resolved-disable-event-sources-before-unreffing-them.patch

Status in systemd package in Ubuntu:
  Won't Fix
Status in systemd source package in Focal:
  Won't Fix

Bug description:
  [impact]

  The initial patch for LP: #1934221 was not sufficient to fix the root
  cause of the segfault, but rather moved it to a slightly different
  location in the code (still inside the on_query_timeout handler).

  [test case]

  this bug is only to revert the previous patch

  For verification we should keep systemd-resolved running for a while and observe that it does not crash, using the relevant configuration in addition to being able to resolve DNS queries as expected, e.g.:
  ```
  root at ff-vm:~# cat /etc/systemd/resolved.conf
  [Resolve]
  DNS=46.182.19.48#dns2.digitalcourage.de 1.1.1.1#cloudflare-dns.com 9.9.9.9#dns.quad9.net
  DNSSEC=yes
  DNSOverTLS=opportunistic
  MulticastDNS=no
  LLMNR=no
  Cache=yes
  DNSStubListener=yes
  Domains=~.
  root at ff-vm:~# dmesg | grep segfault
  root at ff-vm:~# dmesg | grep "systemd-resolve"
  root at ff-vm:~# resolvectl query google.com
  google.com: 2a00:1450:4001:809::200e -- link: enp5s0
              172.217.18.110 -- link: enp5s0

  -- Information acquired via protocol DNS in 177.4ms.
  -- Data is authenticated: no
  ```

  [regression potential]

  Any regression could cause crashes in systemd-resolved, making it
  unresponsive to DNS network name requests to local applications.

  
  [other info]

  this only reverts the patch that was added for LP: #1934221, as this
  patch was detected to still produce (slightly different) segfaults in
  on_query_timeout
  (https://errors.ubuntu.com/problem/c4e5be3f1c7af9483993c7e6007b9325ab5b78cd),
  similar to the original segfaults in on_query_timeout
  (https://errors.ubuntu.com/problem/bb0ce4ff8e6ef86041cfb5647b792823a20b44f7)

  We want to revert the patch in Focal (systemd v245) for now, while we'll try to fix the root cause in Hirsute (systemd v247), adding more relevant patches that were added to systemd-stable v247 (but not systemd-stable v245):
  https://github.com/systemd/systemd-stable/commits/v247-stable/src/resolve/resolved-dns-query.c
  https://github.com/systemd/systemd-stable/commit/64317106aed94a6fb758ab6b08ba490873fc5227
  https://github.com/systemd/systemd-stable/commit/91ba2eac4b6b463026b3a93e5a139923e8f2cfe4
  https://github.com/systemd/systemd-stable/commit/ab9f7e1a51005f12d3bac83b86716d9d33048eb7
  https://github.com/systemd/systemd-stable/commit/78a43c33c8847ebbc2d3cf530ebe304924c58b32
  https://github.com/systemd/systemd-stable/commit/c8d7fab2286384b19ff6328cece107c4c02d7bb8

  => Root-causing this issue will be done in the (re-opened) LP:
  #1934221

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