Package: systemd
Severity: serious
In debian, tmp.mount is disabled through a distro-patch by default. It
means we don't want user's system to get /tmp on tmpfs without explicit
enablement (either by enabling tmp.mount unit or via fstab).
We noticed that starting an unit using "PrivateTmp=yes" will pull
tmp.mount (which mounts /tmp on tmpfs) in its requirements chain (even
if this unit is condition fail).
For instance:
systemctl show -p Requires -p RequiresMountsFor systemd-timesyncd.service
Requires=-.mount tmp.mount
RequiresMountsFor=/var/lib/systemd/clock /tmp /var/tmp
Note that multiple units are using the private tmp feature like cups.
Also, if the unit is restarted (like an upgrade involving cups), /tmp
will as well be remounted as tmpfs, which can wipe /tmp content to new
process and get some annoying side-effects.
We need to find a way to ensure that tmp.mount is never accidentally
trigger, while still enabling the user using fstab to enable /tmp as
tmpfs. Enabling the unit to get the same effect would be a nice addition.
