libuser uses fnctl locking for files in /etc, but shadow-utils uses .lock files. Therefore, the two approaches do not achieve mutual exclusion. This is based on shadow-utils 2:4.1.5.1-1 and libuser 0.57.7-1.
Thanks for your report. (Fixing this should also allow us to better fix #454646 and #454443.)
This bug appears to have been reported against 'rawhide' during the Fedora 19 development cycle. Changing version to '19'. (As we did not run this process for some time, it could affect also pre-Fedora 19 development cycle bugs. We are very sorry. It will help us with cleanup during Fedora 19 End Of Life. Thank you.) More information and reason for this action is here: https://fedoraproject.org/wiki/BugZappers/HouseKeeping/Fedora19
Still present in libuser-0.60.
*** Bug 1148008 has been marked as a duplicate of this bug. ***
This bug appears to have been reported against 'rawhide' during the Fedora 23 development cycle. Changing version to '23'. (As we did not run this process for some time, it could affect also pre-Fedora 23 development cycle bugs. We are very sorry. It will help us with cleanup during Fedora 23 End Of Life. Thank you.) More information and reason for this action is here: https://fedoraproject.org/wiki/BugZappers/HouseKeeping/Fedora23
*** This bug has been marked as a duplicate of bug 1246225 ***