This was recently reported in launchpad at:

https://bugs.launchpad.net/ubuntu/+source/samba/+bug/759711

I have attached the stacktrace:

Thread 1 (Thread 9458):
#0  0x00007f54d40a2d05 in raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
        resultvar = 0
        pid = <value optimized out>
        selftid = 9458
#1  0x00007f54d40a6ab6 in abort () at abort.c:92
        save_stage = 2
        act = {__sigaction_handler = {sa_handler = 0x7f54d98be830, sa_sigaction = 0x7f54d98be830}, sa_mask = {__val = {140002403805232, 140002403805332, 140002403805232, 140002403805332, 0, 0, 0, 0, 0, 19657935440, 7795575241274556416, 140002311417216, 140002402960208, 0, 32, 0}}, sa_flags = 0, sa_restorer = 0}
        sigs = {__val = {32, 0 <repeats 15 times>}}
#2  0x00007f54d6ff1960 in dump_core () at lib/fault.c:337
        called = true
        __FUNCTION__ = "dump_core"
#3  0x00007f54d72fc1bc in exit_server_common (how=<value optimized out>, reason=<value optimized out>) at smbd/server.c:902
        oldlevel = 1
        had_open_conn = <value optimized out>
        sconn = 0x0
        __FUNCTION__ = "exit_server_common"
#4  0x00007f54d72fc661 in exit_server (explanation=0x24f2 <Address 0x24f2 out of bounds>) at smbd/server.c:926
No locals.
#5  0x00007f54d72fd44d in main (argc=<value optimized out>, argv=<value optimized out>) at smbd/server.c:1310
        is_daemon = <value optimized out>
        interactive = <value optimized out>
        Fork = <value optimized out>
        no_process_group = <value optimized out>
        log_stdout = false
        ports = 0x0
        profile_level = 0x0
        opt = <value optimized out>
        pc = <value optimized out>
        print_build_options = false
        long_options = {{longName = 0x0, shortName = 0 '\000', argInfo = 4, arg = 0x7f54d4c4b1e0, val = 0, descrip = 0x7f54d7502de0 "Help options:", argDescrip = 0x0}, {longName = 0x7f54d740f196 "daemon", shortName = 68 'D', argInfo = 0, arg = 0x0, val = 1000, descrip = 0x7f54d7502dee "Become a daemon (default)", argDescrip = 0x0}, {longName = 0x7f54d7502e08 "interactive", shortName = 105 'i', argInfo = 0, arg = 0x0, val = 1001, descrip = 0x7f54d7503418 "Run interactive (not a daemon)", argDescrip = 0x0}, {longName = 0x7f54d7502e14 "foreground", shortName = 70 'F', argInfo = 0, arg = 0x0, val = 1002, descrip = 0x7f54d7503438 "Run daemon in foreground (for daemontools, etc.)", argDescrip = 0x0}, {longName = 0x7f54d7502e1f "no-process-group", shortName = 0 '\000', argInfo = 0, arg = 0x0, val = 1003, descrip = 0x7f54d7503470 "Don't create a new process group", argDescrip = 0x0}, {longName = 0x7f54d7502e30 "log-stdout", shortName = 83 'S', argInfo = 0, arg = 0x0, val = 1004, descrip = 0x7f54d7502e3b "Log to stdout", argDescrip = 0x0}, {longName = 0x7f54d7502e49 "build-options", shortName = 98 'b', argInfo = 0, arg = 0x0, val = 98, descrip = 0x7f54d7502e57 "Print build options", argDescrip = 0x0}, {longName = 0x7f54d738a4d1 "port", shortName = 112 'p', argInfo = 1, arg = 0x7fff93b44f08, val = 0, descrip = 0x7f54d7502e6b "Listen on the specified ports", argDescrip = 0x0}, {longName = 0x7f54d7502e89 "profiling-level", shortName = 80 'P', argInfo = 1, arg = 0x7fff93b44f00, val = 0, descrip = 0x7f54d7502e99 "Set profiling level", argDescrip = 0x7f54d7502ead "PROFILE_LEVEL"}, {longName = 0x0, shortName = 0 '\000', argInfo = 4, arg = 0x7f54d77f6ac0, val = 0, descrip = 0x7f54d7502ebb "Common samba options:", argDescrip = 0x0}, {longName = 0x0, shortName = 0 '\000', argInfo = 4, arg = 0x7f54d77dcd00, val = 0, descrip = 0x7f54d7503498 "Build-time configuration overrides:", argDescrip = 0x0}, {longName = 0x0, shortName = 0 '\000', argInfo = 0, arg = 0x0, val = 0, descrip = 0x0, argDescrip = 0x0}}
        parent = 0x7f54d98d43c0
        frame = 0x7f54d97ef110
        __FUNCTION__ = "main"