Hello,

Is this is a configuration problem or a bug with imapc or imap;  I would appreciate if you could assist us to debug this further.

A coredump is attached if it helps.

The logs look similar to this:

Jun 01 16:21:13 doveb0-rmt0-cn1 dovecot[75106]: imap(user@domie02.com)<105800><BxSqJw39DLgKZQD+>: Warning: Timeout leak: 0x7f9a92c0c1c0 (imapc-client.c:475)
Jun 01 16:21:13 doveb0-rmt0-cn1 dovecot[75106]: imap(user@domie02.com)<105800><BxSqJw39DLgKZQD+>: Warning: Raw backtrace for leaks: /usr/lib/dovecot/libdovecot.so.0(backtrace_append+0x42) [0x7f9a92a7e872] -> /usr/lib/dovecot/libdovecot.so.0(backtrace_get+0x1e) [0x7f9a92a7e98e] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_destroy+0x2b5) [0x7f9a92aa21e5] -> /usr/lib/dovecot/libdovecot-storage.so.0(imapc_client_run+0x115) [0x7f9a92c0bcb5] -> /usr/lib/dovecot/libdovecot-storage.so.0(imapc_mailbox_run_nofetch+0x20) [0x7f9a92c089f0] -> /usr/lib/dovecot/libdovecot-storage.so.0(imapc_mailbox_sync_init+0x868) [0x7f9a92c0b198] -> /usr/lib/dovecot/libdovecot-storage.so.0(mailbox_sync_init+0x58) [0x7f9a92bbfa68] -> dovecot/imap(imap_sync_init+0x95) [0x5605e4ebbe55] -> dovecot/imap(+0x17343) [0x5605e4ea5343] -> dovecot/imap(cmd_idle+0xb4) [0x5605e4ea5674] -> dovecot/imap(command_exec+0xa4) [0x5605e4eb04d4] -> dovecot/imap(+0x2044f) [0x5605e4eae44f] -> dovecot/imap(+0x204fa) [0x5605e4eae4fa] -> dovecot/imap(client_handle_input+0x1b5) [0x5605e4eae9d5] -> dovecot/imap(client_input+0x70) [0x5605e4eaef40] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_call_io+0x69) [0x7f9a92aa1819] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_handler_run_internal+0x132) [0x7f9a92aa2f02] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_handler_run+0x50) [0x7f9a92aa18c0] -> /usr/lib/dovecot/libdovecot.so.0(io_loop_run+0x40) [0x7f9a92aa1a80] -> /usr/lib/dovecot/libdovecot.so.0(master_service_run+0x13) [0x7f9a92a143c3] -> dovecot/imap(main+0x4fa) [0x5605e4e9ff0a] -> /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xea) [0x7f9a927d2d0a] -> dovecot/imap(_start+0x2a) [0x5605e4e9ffca]
Jun 01 16:23:49 doveb0-rmt0-cn1 dovecot[75106]: imap(user@domie02.com)<105800><BxSqJw39DLgKZQD+>: Fatal: master: service(imap): child 105800 killed with signal 11 (core dumped)

# 2.3.20 (80a5ac675d): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.5.20 (149edcf2)
# OS: Linux 5.10.0-23-amd64 x86_64 Debian 11.7 fuse.glusterfs
# Hostname: doveb0-rmt0-cn1
auth_cache_negative_ttl = 5 mins
auth_cache_size = 50 M
auth_default_realm = domie02.com
auth_master_user_separator = *
auth_mechanisms = plain login
auth_verbose = yes
auth_worker_max_count = 16
disable_plaintext_auth = no
first_valid_uid = 499
hostname = smtp.domie02.com
imapc_features = fetch-bodystructure fetch-headers rfc822.size search modseq acl delay-login
imapc_host = 10.101.0.250
imapc_max_idle_time = 5 mins
imapc_password = # hidden, use -P to show it
imapc_sasl_mechanisms = plain login
imapc_ssl = starttls
imapc_ssl_verify = no
last_valid_uid = 499
lda_mailbox_autocreate = yes
lda_mailbox_autosubscribe = yes
login_greeting = You have successfully logged in to domie02.com IMAP server
login_trusted_networks = 10.101.0.74 10.101.0.73
mail_always_cache_fields = flags hdr.* date.received date.sent
mail_cache_fields = flags date.received guid size.physical size.virtual imap.bodystructure body.snippet
mail_debug = yes
mail_fsync = always
mail_location = mdbox:/var/vmail/%d/%n/mdbox:VOLATILEDIR=/dev/shm/dovecot/%2.256Nu/%d/%n
mail_plugins = " notify mail_log zlib acl"
mail_privileged_group = mail
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 index ihave duplicate mime foreverypart extracttext
mdbox_rotate_size = 200 M
mmap_disable = yes
namespace Domie02 {
  list = children
  location = imapc:/var/vmail/%d/%n/shared/indexes/%%n:INDEXPVT=/var/vmail/%d/%n/shared-pvt/%%n:VOLATILEDIR=/dev/shm/dovecot/%2.256Nu/%d/%n/%%n
  prefix = shared.%%n.
  separator = .
  subscriptions = no
  type = shared
}
namespace inbox {
  inbox = yes
  location = 
  mailbox Drafts {
    special_use = \Drafts
  }
  mailbox Junk {
    special_use = \Junk
  }
  mailbox Sent {
    special_use = \Sent
  }
  mailbox "Sent Messages" {
    special_use = \Sent
  }
  mailbox Spam.Virus {
    auto = subscribe
  }
  mailbox Spam {
    auto = subscribe
  }
  mailbox Trash {
    special_use = \Trash
  }
  prefix = 
  separator = .
  subscriptions = yes
  type = private
}
passdb {
  args = password=#hidden_use-P_to_show#
  driver = static
  master = yes
  override_fields = allow_real_nets=127.0.0.0/8,local,10.101.0.74,10.101.0.73 userdb_acl_user=%{auth_user} userdb_namespace/Domie02/disabled=yes
  result_success = continue
}
passdb {
  args = password=#hidden_use-P_to_show#
  driver = static
  override_fields = allow_real_nets=127.0.0.0/8,local,10.101.0.74,10.101.0.73
  result_success = continue
}
passdb {
  args = /etc/dovecot/dovecot-ldap-users.conf.ext
  driver = ldap
}
passdb {
  args = /etc/dovecot/dovecot-ldap-groups.conf.ext
  driver = ldap
}
plugin {
  acl = vfile:/etc/dovecot/global-acls/%d/master-dovecot-acl:cache_secs=300
  acl_defaults_from_inbox = yes
  acl_globals_only = no
  acl_shared_dict = file:/var/dovecot-acl/%d/shared-mailboxes.db
  imap_compress_deflate_level = 6
  mail_log_events = flag_change
  mail_log_fields = uid box flags
  sieve = file:~/sieve;active=~/sieve/%n.sieve
  sieve_before = /var/vmail/global-sieve/global.sieve
  sieve_env_email_address = %u
  sieve_env_mailbox_prefix = %{userdb:mailbox_prefix}
  sieve_global = /var/vmail/sieve
  sieve_global_extensions = +editheader +vnd.dovecot.environment
  zlib_save = zstd
  zlib_save_level = 5
}
protocols = " imap lmtp sieve submission"
service auth-worker {
  user = dovecot
}
service auth {
  unix_listener auth-userdb {
    group = mail
    mode = 0666
    user = vmail
  }
}
service doveadm {
  inet_listener dovadm-dom-mgmt {
    address = 10.100.1.71
    port = 8080
    ssl = no
  }
  inet_listener dovadm-dom {
    address = 10.101.0.71
    port = 8080
    ssl = no
  }
  vsz_limit = 256 M
}
service imap-login {
  inet_listener imap-dom {
    address = 10.101.0.71
    port = 143
    ssl = no
  }
  inet_listener imap {
    port = 0
  }
  inet_listener imaps-dom {
    address = 10.101.0.71
    port = 993
    ssl = yes
  }
  inet_listener imaps {
    port = 0
  }
  process_limit = 400
  process_min_avail = 2
  service_count = 20
  vsz_limit = 512 M
}
service imap {
  process_limit = 2048
  process_min_avail = 0
  service_count = 1
  vsz_limit = 4 G
}
service lmtp {
  inet_listener lmtp-dom {
    address = 10.101.0.71
    port = 24
    ssl = no
  }
  process_limit = 0
  process_min_avail = 0
  service_count = 0
  unix_listener lmtp {
    mode = 0666
  }
  vsz_limit = 256 M
}
service managesieve-login {
  inet_listener sieve-dom {
    address = 10.101.0.71
    port = 4190
    ssl = no
  }
  inet_listener sieve {
    port = 0
  }
  process_limit = 0
  process_min_avail = 0
  service_count = 0
  vsz_limit = 64 M
}
service managesieve {
  process_limit = 1024
  process_min_avail = 0
  service_count = 1
  vsz_limit = 256 M
}
service submission-login {
  inet_listener submission-dom {
    address = 10.101.0.71
    port = 587
    ssl = no
  }
  inet_listener submission {
    port = 0
  }
  inet_listener submissions-dom {
    address = 10.101.0.71
    port = 465
    ssl = yes
  }
  process_limit = 250
  process_min_avail = 2
  service_count = 1
  vsz_limit = 256 M
}
service submission {
  process_limit = 1024
  process_min_avail = 0
  service_count = 1
  vsz_limit = 256 M
}
ssl = required
ssl_cert = </etc/ssl/certs/doveb0-rmt0-cn1.mail.rmt.domie02.com.pem
ssl_client_ca_dir = /etc/ssl/certs
ssl_key = # hidden, use -P to show it
submission_max_mail_size = 30000 k
submission_relay_host = 10.101.0.7
submission_relay_port = 587
submission_relay_ssl = starttls
submission_relay_ssl_verify = no
submission_relay_trusted = yes
userdb {
  driver = prefetch
}
userdb {
  args = /etc/dovecot/dovecot-ldap-users.conf.ext
  driver = ldap
}
userdb {
  args = /etc/dovecot/dovecot-ldap-groups.conf.ext
  driver = ldap
}
protocol lmtp {
  mail_plugins = " notify mail_log zlib acl sieve acl"
}
protocol lda {
  mail_plugins = " notify mail_log zlib acl sieve acl"
}
protocol imap {
  mail_max_userip_connections = 100
  mail_plugins = " notify mail_log zlib acl"
}
protocol sieve {
  mail_max_userip_connections = 40
}
protocol submission {
  mail_max_userip_connections = 70
}
local 10.101.0.71 {
  doveadm_allowed_commands = 
  doveadm_password = # hidden, use -P to show it
}
local 10.100.1.71 {
  doveadm_allowed_commands = 
  doveadm_password = # hidden, use -P to show it
}