Comment 7 for bug 1571531

/etc/ld.so.preload should be a site-specific file (ie, it shouldn't come from Ubuntu). I wouldn't want to break people by adding an explicit deny, but I'd prefer users encountering this to update their /etc/apparmor.d/local/usr.sbin.cupsd file to have:

/etc/ld.so.preload r,

Or if people just want to silence it and not allow it:

deny /etc/ld.so.preload r,

Then run: sudo apparmor_parser -r /etc/apparmor.d/usr.sbin.cupsd
(note, that the file to apparmor_parser is not the one that was modified)