rsyncd running by non-super-user tries to change gid

[schwitin]

rsync version 3.1.3 protocol version 31

Steps to reproduce

rsyncd.conf:

use chroot = false strict modes = false hosts allow = * log file = /var/log/rsync/rsyncd.log pid file = /run/rsyncd.pid uid = root gid = root ...

Run rsyncd as not privileged user

Copy a file to remote server:
/usr/bin/rsync /path/to/myfile.zip rsync://myhost/my-module/new-folder/

Actual behavior

On The clinet side

@ERROR: setgroups failed rsync error: error starting client-server protocol (code 5) at main.c(1675) [sender=3.1.3]

On the server side (rsyncd.log)
2024/06/13 14:15:03 [42616] rsync: setgroups failed: Operation not permitted (1)

Expected behavior

https://download.samba.org/pub/rsync/rsyncd.conf.5#gid

gid The default for a non-super-user is to not change any group attributes (and indeed, your OS may not allow a non-super-user to try to change their group settings).

Workaround: remove uid and gid from rsyncd.conf