sysctl.d file is misnamed and unneeded

[Dan Streetman]

[impact]

the sysctl.d file /usr/lib/sysctl.d/protect-links.conf is misnamed, due to lacking the expected leading number to order it. This results in it being evaluated after all other number-prefixed conf files, effectively overriding any conflicting configuration in the other files, including any admin-provided files in /etc/sysctl.d.

Additionally, this file should not be included at all, as (unlike Debian) Ubuntu assumes systemd will always be installed, thus the sysctl settings from this file will be provided by the systemd-provided sysctl config files.

[test case]

create a file, e.g. /etc/sysctl.d/99-test.conf, with any config that also exists in /usr/lib/sysctl.d/protect-links.conf but with a different setting, and reboot, then check which value was used.

[regression potential]

any regression would likely result in incorrect or unexpected values for the sysctls contained in this conf file

[scope]

this is needed in f and later

this file is not present in b

however, see other info

[other info]

while this bug exists in f and later, it's also trivial to work around it (though not obvious) by renaming the manual configuration file, e.g. instead of using /etc/sysctl.d/99-custom.conf a local admin should instead use /etc/sysctl.d/z-custom.conf so the custom file is lexically after 'protect-links.conf'.

Since removing the file entirely could result in a change in behavior, if the local admin has explicitly modified the file or taken other steps, and since it's trivial (though again, not obvious) to override the file lexically, this seems like it should not be SRUed, but only fixed in the development release.

Also, since Debian's policy does allow for systems that do *not* use systemd, I'm not opening a bug against Debian to remove the file.

[Dan Streetman (ddstreet)]

For clarity, I explicitly added SRU release targets and marked them as either invalid (for bionic, since the file doesn't exist there) or wont-fix (as explained in the description).

[Launchpad Janitor (janitor)]

This bug was fixed in the package procps - 2:3.3.17-5ubuntu3

---------------
procps (2:3.3.17-5ubuntu3) impish; urgency=medium

  * Remove /usr/lib/sysctl.d/protect-links.conf (LP: #1938585)

 -- Dan Streetman <email address hidden> Fri, 30 Jul 2021 12:17:48 -0400