dovecot-2.2.15 process dovecot/imap segfaults when dict process has troubles

[Marcin Mirosław]

Hi!
I hope it's not too late to wish all the best in 2015 year!

I'm writing the email because I've noticed that if dict process has any
troubles with configuration then dovecot/imap throws segfault:
log:
Jan 12 16:51:59 mail dovecot: dict: Error: Failed to initialize
dictionary 'lastlogin': dict pgsql: Can't open configuration file
/etc/dovecot/dovecot-dict-sql.conf.ext: Permission denied
Jan 12 16:51:59 mail dovecot: dict: Error: Failed to initialize
dictionary 'lastlogin': dict pgsql: Can't open configuration file
/etc/dovecot/dovecot-dict-sql.conf.ext: Permission denied
Jan 12 16:52:00 mail dovecot: master: Error: service(imap): child 24243
killed with signal 11 (core dumped)

and here is backtrace:
(gdb) bt
#0  io_remove_full (_io=0x7fb02b0afce0, closed=false) at ioloop.c:119
#1  0x00007fb02aac5f40 in io_remove (io=<optimized out>) at ioloop.c:154
#2  0x00007fb02aa841b2 in client_dict_finish_transaction
(dict=dict at entry=0x7fb02b0afc20, id=<optimized out>, ret=ret at entry=-1)
at dict-client.c:274
#3  0x00007fb02aa84286 in client_dict_disconnect
(dict=dict at entry=0x7fb02b0afc20) at dict-client.c:459
#4  0x00007fb02aa8493d in client_dict_deinit (_dict=0x7fb02b0afc20) at
dict-client.c:519
#5  0x00007fb02aa28ece in last_login_dict_deinit (user=<optimized out>)
at last-login-plugin.c:34
#6  0x00007fb02aa28f92 in last_login_user_deinit (user=0x7fb02b0ab400)
at last-login-plugin.c:46
#7  0x00007fb02ab820bf in mail_user_unref
(_user=_user at entry=0x7fb02b0bbdc8) at mail-user.c:163
#8  0x00007fb02ac1ee0d in client_default_destroy (client=0x7fb02b0bbd50,
reason=<optimized out>) at imap-client.c:284
#9  0x00007fb02ac29549 in client_kill_idle (client=0x7fb02b0bbd50) at
main.c:105
#10 0x00007fb02ac296a5 in client_kill_idle (client=0x7fb02b0bbd50) at
main.c:129
#11 imap_die () at main.c:121
#12 0x00007fb02aac661d in io_loop_call_io (io=0x7fb02b093ce0) at
ioloop.c:498
#13 0x00007fb02aac7a15 in io_loop_handler_run_internal
(ioloop=ioloop at entry=0x7fb02b091740) at ioloop-epoll.c:220
#14 0x00007fb02aac66d5 in io_loop_handler_run
(ioloop=ioloop at entry=0x7fb02b091740) at ioloop.c:545
#15 0x00007fb02aac677a in io_loop_run (ioloop=0x7fb02b091740) at
ioloop.c:522
#16 0x00007fb02aa5b5aa in master_service_run (service=0x7fb02b0915d0,
callback=<optimized out>) at master-service.c:566
#17 0x00007fb02ac116cd in main (argc=<optimized out>, argv=<optimized
out>) at main.c:412

Marcin