smbd crashed with SIGABRT in push_ucs2_talloc()/lp_servicename returns NULL

StacktraceTop:
 push_ucs2_talloc (ctx=0x0, dest=0x7fffd97a7b68, src=0x0, converted_size=0x7fffd97a7b60) at lib/charcnv.c:1160
 E_md4hash (passwd=0x0, p16=0x7fffd97a7ca0 "\b") at ../libcli/auth/smbencrypt.c:78
 create_volume_objectid (conn=<optimized out>, objid=0x7fffd97a7ca0 "\b") at smbd/trans2.c:2885
 call_nt_transact_ioctl (max_data_count=64, data_count=64, ppdata=<optimized out>, setup_count=<optimized out>, ppsetup=<optimized out>, req=0x7f9f5c96da20, conn=0x7f9f5c8a1a00, ppparams=<optimized out>, parameter_count=<optimized out>) at smbd/nttrans.c:2205
 handle_nttrans (conn=0x7f9f5c8a1a00, state=<optimized out>, req=0x7f9f5c96da20) at smbd/nttrans.c:2904

Status changed to 'Confirmed' because the bug affects multiple users.

Function:

unsigned char *create_volume_objectid(connection_struct *conn, unsigned char objid[16])
{
    E_md4hash(lp_servicename(SNUM(conn)),objid);
    return objid;
}

lp_servicename returning NULL Is the same problem as seen in bug 913809 - might be related.

Please could reporters of this issue set the log level to 5:

    log level 5

in /etc/samba/smb.conf, reload smbd and try to reproduce again - hopefully samba will provide some useful debug messages which might help ID whats going on.

The output of:

   sudo testparm -s

would also be helpful.

$ sudo testparm -s
Load smb config files from /etc/samba/smb.conf
rlimit_max: increasing rlimit_max (1024) to minimum Windows limit (16384)
Processing section "[printers]"
Processing section "[print$]"
Loaded services file OK.
Server role: ROLE_STANDALONE
[global]
 server string = %h server (Samba, Ubuntu)
 map to guest = Bad User
 obey pam restrictions = Yes
 pam password change = Yes
 passwd program = /usr/bin/passwd %u
 passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* .
 unix password sync = Yes
 syslog = 0
 log file = /var/log/samba/log.%m
 max log size = 1000
 dns proxy = No
 usershare allow guests = Yes
 panic action = /usr/share/samba/panic-action %d
 idmap config * : backend = tdb

[printers]
 comment = All Printers
 path = /var/spool/samba
 create mask = 0700
 printable = Yes
 print ok = Yes
 browseable = No

[print$]
 comment = Printer Drivers
 path = /var/lib/samba/printers

[Expired for samba (Ubuntu) because there has been no activity for 60 days.]