bug#63245: Potential regression: cp --preserve=mode or --preserve=all fails to copy files from subdirectory

[Schlomo Schapiro]

Hello,

I'm a maintainer of the Relax-and-Recover (https://relax-and-recover.org/)
Open Source project and think that I might have found a major regression in
cp, starting somewhere with version 9.

Please see https://bugs.launchpad.net/ubuntu/+source/coreutils/+bug/2017414
and https://github.com/rear/rear/issues/2972 for how I found out about this.

Problem:

We use a cp call like the following to copy various files and directory
into a destination path with preserving the structure:

cp --verbose -t DESTINATION -L --preserve=all --parents SOURCE...

Over the last 10+ years that worked well on all Linux distros (ReaR is
build for and tested on nearly all distros), but I recently found out that
on Ubuntu 23.04 this fails like this:

# rm -Rf /tmp/f && mkdir /tmp/f && cp --verbose -t /tmp/f -L --preserve=all
--parents /etc/apt/sources.list && echo yes ; ls -lR
/tmp/f/etc/apt/sources.list
/etc/apt/sources.list
/etc -> /tmp/f/etc
/etc/apt -> /tmp/f/etc/apt
'/etc/apt/sources.list' -> '/tmp/f/etc/apt/sources.list'
cp: ‘etc/apt’: No such file or directory
-rw-r--r-- 1 root root 2437 Apr 23 09:53 /etc/apt/sources.list
-rw-r--r-- 1 root root 2437 Apr 23 09:53 /tmp/f/etc/apt/sources.list
#

Ubuntu 23.04 uses cp (GNU coreutils) 9.1

On Ubuntu 22.04 there is cp (GNU coreutils) 8.32 and the same example works
as expected:

# rm -Rf /tmp/f && mkdir /tmp/f && cp --verbose -t /tmp/f -L --preserve=all
--parents /etc/apt/sources.list && echo yes ; ls -lR
/tmp/f/etc/apt/sources.list /etc/apt/sources.list
/etc -> /tmp/f/etc
/etc/apt -> /tmp/f/etc/apt
'/etc/apt/sources.list' -> '/tmp/f/etc/apt/sources.list'
yes
-rw-r--r-- 1 root root 263 Mär 26 15:20 /etc/apt/sources.list
-rw-r--r-- 1 root root 263 Mär 26 15:20 /tmp/f/etc/apt/sources.list
#

BTW, I checked also on many other distros that ReaR supports and all
distros with cp version 9.1 fail in the same way.

Can you please have a look and advise how to proceed? We at the ReaR
project can of course change our code to use tar for example, but I won't
be surprised if other users will also meet this changed behaviour and maybe
it is indeed a bug.

Kind regards,
Schlomo Schapiro