Comment 3 for bug 1723956

Thanks. Loading busybox-static-dbgsym and retracing this with gdb, I see the following backtrace:

(gdb) thread apply all bt full

Thread 1 (Thread 0x11bb880 (LWP 31592)):
#0 0x0000000000000000 in ?? ()
No symbol table info available.
#1 0x00007f601bb0af90 in __pthread_initialize_minimal_internal ()
   from /lib/x86_64-linux-gnu/libpthread.so.0
No symbol table info available.
#2 0x00007f601bb0a571 in _init () from /lib/x86_64-linux-gnu/libpthread.so.0
No symbol table info available.
#3 0x00007f601c358f70 in ?? ()
No symbol table info available.
#4 0x00000000004f147a in call_init.part ()
No symbol table info available.
#5 0x00000000004f1635 in _dl_init ()
No symbol table info available.
#6 0x00000000004e3a46 in dl_open_worker ()
No symbol table info available.
#7 0x00000000004e11f4 in _dl_catch_error ()
No symbol table info available.
#8 0x00000000004e33b9 in _dl_open ()
No symbol table info available.
#9 0x000000000049ff22 in do_dlopen ()
No symbol table info available.
---Type <return> to continue, or q <return> to quit---
#10 0x00000000004e11f4 in _dl_catch_error ()
No symbol table info available.
#11 0x00000000004a010e in __libc_dlopen_mode ()
No symbol table info available.
#12 0x0000000000493aa8 in __nss_next2 ()
No symbol table info available.
#13 0x000000000048b310 in gethostbyaddr_r ()
No symbol table info available.
#14 0x000000000048d158 in gni_host_inet_name.isra ()
No symbol table info available.
#15 0x000000000048d752 in getnameinfo ()
No symbol table info available.
#16 0x000000000058c312 in sockaddr2str (sa=0x11bdc50, flags=flags@entry=10)
    at libbb/xconnect.c:439
        host = "8.8.8.8\000\000\334\033\001", '\000' <repeats 20 times>, "\350\003\000\000\000\000\000\000\261tB\000\000\000\000\000\002\000\000\000\000\000\000\000\b\000\000\000\000\000\000\000\240\064\203\230\377\177\000\000\372\316B\000\000\000\000\000\003\000\000\000\000\000\000\000\240\064\203\230\377\177\000\000\220\064\203\230\377\177\000\000\372\235O\000\000\000\000\000\003\000\000\000\000\000\000\000K\303X\000\000\000\000"
        serv = "0\000\000\000\000\000\000\000\000K~\000\000\000\000"
        rc = <optimized out>
        salen = <optimized out>
---Type <return> to continue, or q <return> to quit---
#17 0x000000000058caf0 in xmalloc_sockaddr2hostonly_noport (sa=<optimized out>)
    at libbb/xconnect.c:476
No locals.
#18 0x000000000050eb64 in print_host (hostname=<optimized out>,
    header=header@entry=0x5c187f "Server:") at networking/nslookup.c:92
        dotted = 0x11be080 "8.8.8.8"
        revhost = <optimized out>
        cur = 0x11bdc20
        cnt = 0
        result = 0x11bdc20
        rc = 0
        hint = {ai_flags = 0, ai_family = 0, ai_socktype = 1, ai_protocol = 0,
          ai_addrlen = 0, ai_addr = 0x0, ai_canonname = 0x0, ai_next = 0x0}
#19 0x000000000050ec15 in server_print () at networking/nslookup.c:129
        server = <optimized out>
        sa = <optimized out>
#20 nslookup_main (argc=<optimized out>, argv=0x7fff988337a0)
    at networking/nslookup.c:189
No locals.
#21 0x00000000004f890e in run_applet_no_and_exit (applet_no=<optimized out>,
    argv=argv@entry=0x7fff988337a0) at libbb/appletlib.c:759
        argc = <optimized out>
#22 0x00000000004f8aa8 in run_applet_and_exit (name=0x7fff988344df "nslookup",
---Type <return> to continue, or q <return> to quit---
    argv=argv@entry=0x7fff988337a0) at libbb/appletlib.c:766
        applet = <optimized out>
#23 0x00000000004f8d19 in busybox_main (argv=0x7fff988337a0)
    at libbb/appletlib.c:728
No locals.
#24 run_applet_and_exit (name=<optimized out>, argv=argv@entry=0x7fff98833798)
    at libbb/appletlib.c:768
        applet = <optimized out>
#25 0x00000000004f8ede in main (argc=<optimized out>, argv=0x7fff98833798)
    at libbb/appletlib.c:823
No locals.
(gdb)

I think this may map to https://errors.ubuntu.com/problem/c7906cb4fb8d9ab7fa9b995d00b3565b2eddccd4 on the error tracker, which interestingly enough is reported only on 17.04 (zesty).

The stack trace points into the NSS modules used behind gethostbyaddr_r(). I'm unclear why the nslookup tool would be using NSS, but maybe we can understand the bug better by looking at this. Can you attach the /etc/nsswitch.conf file from the affected system?

Can you also confirm the version of the libc6 package you have installed when this happens?