dovecot - Sep 2013 - Panic: file mail-storage.c: line 834 (mailbox_verify_name): assertion failed

Hello List!

I've encountered an error after upgrading my system and dovecot. I guess
it's probably a result of a configuration problem, however after quite some
tinkering with configuration I am still missing the source of the problem.

Sep 28 16:57:21 shwurzbung dovecot: imap(wizz): Panic: file mail-storage.c: line
834 (mailbox_verify_name): assertion failed: (strncmp(vname, ns->prefix,
ns->prefix_len-1) == 0)
Sep 28 16:57:21 shwurzbung dovecot: imap(wizz): Fatal: master: service(imap):
child 23203 killed with signal 6 (core not dumped - set service imap {
drop_priv_before_exec=yes })

The problem above appears with both dovecot 2.2.5 and 2.2.6. It did not happen
while using dovecot 2.1.12.
Operating system is OpenBSD 5.4-current and AMD64. FS type is FFS (default for
OpenBSD).

Output of dovecot -n:

# 2.2.6: /etc/dovecot/dovecot.conf
# OS: OpenBSD 5.4 amd64  
auth_mechanisms = plain login
default_process_limit = 200
managesieve_notify_capability = mailto
managesieve_sieve_capability = fileinto reject envelope encoded-character
vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy
include variables body enotify environment mailbox date ihave
mbox_write_locks = fcntl
mmap_disable = yes
namespace {
  hidden = yes
  inbox = yes
  list = no
  location = mbox:~/mail:INBOX=/var/mail/%u
  prefix = inbox/
  type = private
}
namespace inbox {
  location = 
  mailbox Drafts {
    special_use = \Drafts
  }
  mailbox Junk {
    special_use = \Junk
  }
  mailbox Sent {
    special_use = \Sent
  }
  mailbox "Sent Messages" {
    special_use = \Sent
  }
  mailbox Trash {
    special_use = \Trash
  }
  prefix = 
}
passdb {
  driver = bsdauth
}
plugin {
  sieve = ~/.dovecot.sieve
  sieve_dir = ~/sieve
}
pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
protocols = imap pop3 lmtp sieve
service auth {
  unix_listener /var/run/dovecot/auth-master {
    group = virtuals
    mode = 0600
    user = virtuals
  }
  unix_listener /var/spool/postfix/private/auth {
    mode = 0660
    user = _postfix
  }
  user = root
}
service managesieve-login {
  inet_listener sieve {
    port = 4190
  }
  inet_listener sieve_deprecated {
    port = 2000
  }
}
ssl_cert = </etc/ssl/ssl.crt
ssl_key = </etc/ssl/private/ssl.key
userdb {
  driver = passwd
  override_fields = mail_home=/home/%u
}
protocol lmtp {
  mail_plugins = " sieve"
}
protocol lda {
  mail_plugins = " sieve"
}
protocol imap {
  imap_client_workarounds = delay-newmail tb-extra-mailbox-sep tb-lsub-flags
  mail_max_userip_connections = 64
}

Thanks in advance for any pointers to a resolution.

Best regards,
Kamil Andrusz

-- 
It's just a matter of opinion.

On 28.9.2013, at 18.11, Kamil Andrusz <wizz at mniam.net> wrote:
> Sep 28 16:57:21 shwurzbung dovecot: imap(wizz): Panic: file mail-storage.c:
line 834 (mailbox_verify_name): assertion failed: (strncmp(vname, ns->prefix,
ns->prefix_len-1) == 0)
> namespace {
>  hidden = yes
>  inbox = yes
>  list = no
>  location = mbox:~/mail:INBOX=/var/mail/%u
>  prefix = inbox/
>  type = private
> }
Don't use prefix=inbox/. Either use INBOX/ or something completely
different. I think the proper fix here is to just fail to run with this
configuration.