I haven't been able to reproduce this one, but have received a couple of corefiles from end-users:

```
(gdb) bt
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#1  0x00007f6198b5c537 in __GI_abort () at abort.c:79
#2  0x00007f6199e63960 in dump_core () at ../../source3/lib/dumpcore.c:338
#3  0x00007f6199e70f01 in smb_panic_s3 (why=<optimized out>) at ../../source3/lib/util.c:713
#4  0x00007f61993e98ea in smb_panic (why=why@entry=0x7ffdf6039fd0 "Signal 11: Segmentation fault") at ../../lib/util/fault.c:198
#5  0x00007f61993e9971 in fault_report (sig=11) at ../../lib/util/fault.c:82
#6  sig_fault (sig=11) at ../../lib/util/fault.c:93
#7  <signal handler called>
#8  0x00007f6199d55090 in lpcfg_service_ok (service=0x0) at ../../lib/param/loadparm.c:966
#9  0x00007f6199e4488a in lp_do_section (pszSectionName=0x56295345d540 "vr", userdata=userdata@entry=0x0) at ../../source3/param/loadparm.c:2893
#10 0x00007f6199e44ebb in process_smbconf_service (service=0x56295345b530) at ../../source3/param/loadparm.c:2184
#11 process_registry_shares () at ../../source3/param/loadparm.c:2309
#12 0x00007f61998fc9e9 in load_registry_shares () at ../../source3/param/service.c:61
#13 0x0000562952d4b4ca in init_srv_share_info_ctr (p=p@entry=0x5629534620b8, info_ctr=0x562953448f10, resume_handle_p=0x0, total_entries=0x562953462cb0, all_shares=all_shares@entry=true)
    at ../../source3/rpc_server/srvsvc/srv_srvsvc_nt.c:641
#14 0x0000562952d4d515 in _srvsvc_NetShareEnumAll (p=p@entry=0x5629534620b8, r=r@entry=0x56295345a0f0) at ../../source3/rpc_server/srvsvc/srv_srvsvc_nt.c:1720
#15 0x0000562952d5082e in srvsvc__op_dispatch_internal (dce_call=0x5629534474b0, mem_ctx=<optimized out>, r=0x56295345a0f0, dispatch=S3COMPAT_RPC_DISPATCH_EXTERNAL)
    at ./librpc/gen_ndr/ndr_srvsvc_scompat.c:296
#16 0x00007f6199e09374 in dcesrv_request (call=0x5629534474b0) at ../../librpc/rpc/dcesrv_core.c:1957
#17 dcesrv_process_ncacn_packet (blob=..., pkt=<optimized out>, dce_conn=0x562953455100) at ../../librpc/rpc/dcesrv_core.c:2381
#18 dcesrv_loop_next_packet (dce_conn=0x562953455100, pkt=<optimized out>, buffer=...) at ../../librpc/rpc/dcesrv_core.c:2923
#19 0x00007f6199e0a208 in dcesrv_read_fragment_done (subreq=<optimized out>) at ../../librpc/rpc/dcesrv_core.c:2901
#20 0x00007f61993abde7 in dcerpc_read_ncacn_packet_done (subreq=<optimized out>) at ../../librpc/rpc/dcerpc_util.c:630
#21 0x00007f6199ded1d0 in tstream_readv_pdu_readv_done (subreq=<optimized out>) at ../../lib/tsocket/tsocket_helpers.c:320
#22 0x00007f6199debf6a in tstream_readv_done (subreq=<optimized out>) at ../../lib/tsocket/tsocket.c:604
#23 0x00007f619a0b0a62 in tevent_common_invoke_immediate_handler (im=0x56295343fb40, removed=removed@entry=0x0) at ../../lib/tevent/tevent_immediate.c:190
#24 0x00007f619a0b0a8a in tevent_common_loop_immediate (ev=ev@entry=0x56295341d9a0) at ../../lib/tevent/tevent_immediate.c:236
#25 0x00007f619a0b68bc in epoll_event_loop_once (ev=0x56295341d9a0, location=<optimized out>) at ../../lib/tevent/tevent_epoll.c:919
#26 0x00007f619a0b4c27 in std_event_loop_once (ev=0x56295341d9a0, location=0x7f6199d1ce00 "../../source3/rpc_server/rpc_worker.c:1199") at ../../lib/tevent/tevent_standard.c:114
#27 0x00007f619a0af8a4 in _tevent_loop_once (ev=ev@entry=0x56295341d9a0, location=location@entry=0x7f6199d1ce00 "../../source3/rpc_server/rpc_worker.c:1199") at ../../lib/tevent/tevent.c:828
#28 0x00007f6199d194ca in rpc_worker_main (argc=<optimized out>, argv=<optimized out>, daemon_config_name=daemon_config_name@entry=0x562952dae8a1 "rpcd_classic", num_workers=num_workers@entry=5, 
    idle_seconds=idle_seconds@entry=60, get_interfaces=get_interfaces@entry=0x562952d56a50 <classic_interfaces>, get_servers=0x562952d56a60 <classic_servers>, private_data=0x0)
    at ../../source3/rpc_server/rpc_worker.c:1199
#29 0x0000562952cabcfc in main (argc=<optimized out>, argv=<optimized out>) at ../../source3/rpc_server/rpcd_classic.c:93

```
(gdb) p iServiceIndex
$1 = 1
(gdb) p ServicePtrs[iServiceIndex]
$2 = (struct loadparm_service *) 0x0
```

So it's pretty clear that the current service slot is NULL. This NULL gets passed to lpcfg_service_ok() and crashes.

If we skip this check in case of a NULL slot and move along to `add_a_service()` then the NULL slot will be used appropriately and we should be fine.

This ticket is to get a bug number for a merge request.