Dovecot User Listing Error - getpwent() failed: Invalid Argument

[Reuben Farrelly]

Hi,

I'm running dovecot-2.3 git and seeing on 2 of my Dovecot installations, 
the following message logged quite frequently:

Aug 31 16:55:53 lightning.reub.net dovecot[7698]: auth-worker(7707): 
Error: getpwent() failed: Invalid argument
Aug 31 16:55:53 lightning.reub.net dovecot[7698]: replicator: Error: 
User listing returned failure
Aug 31 16:55:53 lightning.reub.net dovecot[7698]: replicator: Error: 
listing users failed, can't replicate existing data

It appears that this could be having an effect on replication, but it's 
unclear because the secondary/replica doesn't see much traffic.

Authentication is via PAM and the system is Gentoo Linux x86_64. passb 
driver = pam, userdb driver = static .

doveadm user -u '*' shows the system users listed twice like this (is 
this a problem?) and then prints:

----
reuben
liam
reuben
liam
<some other users>
Error: User listing returned failure
Fatal: user listing failed
----

To me that doesn't look right.

Can anyone suggest what could be causing this?  I don't recall seeing 
this message some time ago so I suspect it's a recent change in either 
dovecot, or pam or glibc etc..

Thanks,
Reuben