From cecfb6588bc31e2f4f3ca4784984c03db464c764 Mon Sep 17 00:00:00 2001
From: Michal Sekletár <msekleta@redhat.com>
Date: Dec 15 2020 09:45:45 +0000
Subject: sysctl: let's by default increase the numeric PID range from 2^16 to 2^22


This should PID collisions a tiny bit less likely, and thus improve
security and robustness.

2^22 isn't particularly a lot either, but it's the current kernel
limitation.

Bumping this limit was suggested by Linus himself:

https://lwn.net/ml/linux-kernel/CAHk-=wiZ40LVjnXSi9iHLE_-ZBsWFGCgdmNiYZUXn1-V5YBg2g@mail.gmail.com/

Let's experiment with this in systemd upstream first. Downstreams and
users can after all still comment this easily.

Besides compat concern the most often heard issue with such high PIDs is
usability, since they are potentially hard to type. I am not entirely sure though
whether 4194304 (as largest new PID) is that much worse to type or to
copy than 65563.

This should also simplify management of per system tasks limits as by
this move the sysctl /proc/sys/kernel/threads-max becomes the primary
knob to control how many processes to have in parallel.

Resolves: #1744214

patch_name: 0317-sysctl-let-s-by-default-increase-the-numeric-PID-ran.patch
present_in_specfile: true
location_in_specfile: 317
squash_commits: true

---

diff --git a/sysctl.d/50-pid-max.conf b/sysctl.d/50-pid-max.conf
new file mode 100644
index 0000000..3a8393d
--- /dev/null
+++ b/sysctl.d/50-pid-max.conf
@@ -0,0 +1,17 @@
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+
+# See sysctl.d(5) and core(5) for documentation.
+
+# To override settings in this file, create a local file in /etc
+# (e.g. /etc/sysctl.d/90-override.conf), and put any assignments
+# there.
+
+# Bump the numeric PID range to its maximum of 2^22 (from the in-kernel default
+# of 2^16), to make PID collisions less likely.
+kernel.pid_max = 4194304
+
diff --git a/sysctl.d/meson.build b/sysctl.d/meson.build
index 64f6ce9..a95957a 100644
--- a/sysctl.d/meson.build
+++ b/sysctl.d/meson.build
@@ -2,6 +2,7 @@
 
 install_data(
         '50-default.conf',
+        '50-pid-max.conf',
         install_dir : sysctldir)
 
 in_files = []