On Tue, 8 Mar 2022, Serge E. Hallyn wrote
So deluser was doing the right thing, right?
The bug is how you got into this state? Either the adduser for
the high uid should have checked for it being a delegated subuid,
or the adduser which added the subuids to the lower subuid should
have refused when the higher subuid existed as a uid.
As far as I can see, there is no checking for collisions in either
direction: useradd depends on the ranges [UID_MIN,UID_MAX] and
[SUB_UID_MIN,SUB_UID_MAX] not overlapping, and issues a warning if you
assign a static UID outside the specified range.
--
Ben Harris, University of Cambridge Information Services.
