[Dovecot] imap sort assertion failure

[Andrew Garner]

The following error occurred after a "SORT (TO) US-ASCII ALL" command.
  This only seems to happen with "to", all our other tests work as
expected.

Oct  1 20:32:49 dovecot: IMAP(example at example.com):
pool_data_stack_realloc(): stack frame changed
Oct  1 20:32:49 dovecot: IMAP(example at example.com): Raw backtrace:
imap [0x80c5ed1] ->
imap [0x80c5dec] ->
imap [0x80cde63] ->
imap [0x80c43c0] ->
imap(buffer_write+0x85) [0x80c46f5] ->
imap(buffer_append+0x26) [0x80c4766] ->
imap [0x80be2f5] ->
imap(message_header_decode+0x75) [0x80be3d5] ->
imap(message_header_decode_utf8+0x56) [0x80be5f6] ->
imap [0x80903c4] ->
imap(index_mail_get_first_header+0x3e) [0x809125e] ->
imap(mail_get_first_header_utf8+0x26) [0x80b4726] ->
imap [0x809386b] ->
imap [0x8093900] ->
imap [0x809414e] ->
imap(index_sort_list_finish+0x33) [0x80949d3] ->
imap(index_storage_search_next_nonblock+0x3b6) [0x80924a6] ->
imap(mailbox_search_next+0x30) [0x80b5b70] ->
imap(imap_sort+0xdd) [0x806407d] ->
imap(cmd_sort+0x2a4) [0x805d454] ->
imap [0x805e7b9] ->
imap [0x805e862] ->
imap(client_input+0x65) [0x805ee85] ->
imap(io_loop_handler_run+0x162) [0x80cc2a2] ->
imap(io_loop_run+0x28) [0x80cb628] ->
imap(main+0x4ab) [0x806643b] ->
/lib/tls/i686/cmov/libc.so.6(__libc_start_main+0xc
Oct  1 20:32:49 dovecot: child 31161 (imap) killed with signal 6

# dovecot -n
# 1.1.beta2: /etc/dovecot/dovecot.conf
protocols: imap pop3
listen: 127.0.0.1
disable_plaintext_auth: no
login_dir: /var/run/dovecot/login
login_executable(default): /usr/lib/dovecot/imap-login
login_executable(imap): /usr/lib/dovecot/imap-login
login_executable(pop3): /usr/lib/dovecot/pop3-login
first_valid_uid: 89
mail_location: maildir:~/Maildir
mail_debug: yes
mmap_disable: yes
mail_nfs_storage: yes
mail_nfs_index: yes
lock_method: dotlock
mail_executable(default): /usr/lib/dovecot/rawlog /usr/lib/dovecot/imap
mail_executable(imap): /usr/lib/dovecot/rawlog /usr/lib/dovecot/imap
mail_executable(pop3): /usr/lib/dovecot/pop3
mail_plugins(default):
mail_plugins(imap):
mail_plugins(pop3):
mail_plugin_dir(default): /usr/lib/dovecot/modules/imap
mail_plugin_dir(imap): /usr/lib/dovecot/modules/imap
mail_plugin_dir(pop3): /usr/lib/dovecot/modules/pop3
auth default:
  mechanisms: plain cram-md5
  verbose: yes
  debug: yes
  debug_passwords: yes
  passdb:
    driver: sql
    args: /etc/dovecot/dovecot-sql.conf
  userdb:
    driver: sql
    args: /etc/dovecot/dovecot-sql.conf
  socket:
    type: listen
    client:
      path: /var/spool/postfix/private/auth
      mode: 432
      user: postfix
      group: postfix
    master:
      path: /var/run/dovecot/auth-master
      mode: 384
      user: vmail
      group: vmail