2.2.25 dumps core with "Panic: file imap-client.c: line 837 (client_check_command_hangs): assertion failed: (client->io != NULL)"

[Piper Andreas]

Hello,

Dovecot 2.2.25
OS: Solaris 11 (SunOS 5.11 11.3 i86pc i386 i86pc)
Virtualization: VMware
Filesystem: ZFS
active users: ~4000

About once a day Dovecot crashes with
"Panic: file imap-client.c: line 837 (client_check_command_hangs):
assertion failed: (client->io != NULL)"

The log shows in each case:

Aug 29 12:59:00 surz113 dovecot: [ID 583609 mail.crit] imap(username):
Panic: file imap-client.c: line 837 (client_check_command_hangs):
assertion failed: (client->io != NULL)
Aug 29 12:59:00 surz113 dovecot: [ID 583609 mail.error] imap(username):
Error: Raw backtrace: 0xffff80ffb6f3d88d -> 0xffff80ffb6f6ae82 ->
0x41eba0 -> 0x41ecf3 -> 0xffff80ffb6f5d248 -> 0xffff80ffb6f50d2f ->
0xffff80ffb6f519e0 -> 0xffff80ffb6f50dce -> 0xffff80ffb6f50f90 ->
0xffff80ffb6ee3ebb -> 0x42f169 -> 0x41292c
Aug 29 12:59:00 surz113 dovecot: [ID 583609 mail.crit] imap(username):
Fatal: master: service(imap): child 1461 killed with signal 6 (core not
dumped - set service imap { drop_priv_before_exec=yes })

It happens with different users, all with mailbox-sizes of 9 to 17
GByte. The server stops completely for all users with this Panic and is
then restarted automatically from Solaris Service Management.

Find attached the output of 'doveconf -n'.

Please let me know, if you need any more infos.

Thanks for any help on this issue,
Andreas, postmaster at uni-marburg.de
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# 2.2.25 (f5ac02c): /etc/opt/csw/dovecot/dovecot.conf
# OS: SunOS 5.11 i86pc  
auth_cache_negative_ttl = 0
auth_cache_size = 10 M
auth_master_user_separator = *
auth_username_chars = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.-_
auth_username_format = %u
auth_worker_max_count = 1024
base_dir = /var/run/dovecot/
default_vsz_limit = 2 G
first_valid_gid = 30000
first_valid_uid = 30000
mail_location = maildir:%h/.maildir
mail_plugins = " mail_log notify"
mail_privileged_group = mail
namespace {
  hidden = no
  inbox = yes
  list = yes
  location = maildir:%h/.maildir
  prefix = 
  separator = /
  subscriptions = yes
  type = private
}
namespace inbox {
  hidden = yes
  inbox = no
  list = no
  location = maildir:%h/.maildir
  prefix = mail/
  separator = /
  subscriptions = no
  type = private
}
passdb {
  args = /etc/dovecot.deny
  deny = yes
  driver = passwd-file
}
passdb {
  args = <hidden>
  driver = passwd-file
  master = yes
}
passdb {
  args = blocking=yes cache_key=%u%s *
  driver = pam
}
pop3_uidl_format = %08Xv%08Xu
postmaster_address = postmaster at staff.uni-marburg.de
protocols = imap pop3
service auth-worker {
  user = $default_internal_user
}
service auth {
  client_limit = 6000
}
service imap-login {
  process_min_avail = 64
  service_count = 0
}
service imap {
  process_limit = 6000
}
ssl_cert = </etc/opt/csw/ssl/certs/imap.staff.uni-marburg.de.pem
ssl_key = </etc/opt/csw/ssl/private/imap.staff.uni-marburg.de.key
userdb {
  driver = passwd
}
protocol imap {
  mail_max_userip_connections = 25
  ssl_cert = </etc/opt/csw/ssl/certs/imap.staff.uni-marburg.de.pem
  ssl_key = </etc/opt/csw/ssl/private/imap.staff.uni-marburg.de.key
}
protocol pop3 {
  ssl_cert = </etc/opt/csw/ssl/certs/pop.staff.uni-marburg.de.pem
  ssl_key = </etc/opt/csw/ssl/private/pop.staff.uni-marburg.de.key
}
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