Segfault when using doveadm batch -A : kick

[Apollon Oikonomopoulos]

Hi,

Apparently the "kick" doveadm_cmd_ver2 struct lacks a .mail_cmd member 
pointing to an appropriate allocation function, causing a NULL pointer 
dereference when used via `doveadm batch`.

(gdb) bt
#0  0x0000000000000000 in ?? ()
#1  0x0000555555585882 in doveadm_mail_cmd_init (cmd=cmd at entry=0x7fffffffe680, set=0x5555555f2440) at doveadm-mail.c:596
#2  0x0000555555586f68 in cmd_batch_add (argv=<optimized out>, argc=<optimized out>, batchctx=0x555555606538) at doveadm-mail-batch.c:78
#3  cmd_batch_preinit () at doveadm-mail-batch.c:126
#4  0x00005555555854ce in doveadm_mail_cmd_exec () at doveadm-mail.c:632
#5  0x0000555555585e66 in doveadm_mail_cmd (argv=<optimized out>, argc=4, cmd=0x555555602a00) at doveadm-mail.c:748
#6  doveadm_mail_try_run () at doveadm-mail.c:821
#7  0x0000555555575e7f in main () at doveadm.c:404
#8  0x00007ffff74acb17 in __libc_start_main (main=0x555555575990 <main>, argc=5, argv=0x7fffffffea18, init=<optimized out>, fini=<optimized out>, 
    rtld_fini=<optimized out>, stack_end=0x7fffffffea08) at ../csu/libc-start.c:310
#9  0x0000555555575fca in _start () at doveadm-mail.c:1127

(gdb) p *cmd
$5 = {alloc = 0x0, name = 0x5555555bdd0c "kick", usage_args = 0x5555555be738 "[-a <anvil socket path>] <user mask>[|]<ip/bits>"}

(This is Debian bug #915411[1])

Regards,
Apollon

[1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=915411