segfault in update_configuration()

[jaymzh]

This is migrated from https://sourceforge.net/p/concordance/bugs/41/

Downstream reported a segfault. Here's a exerpt from the stacktrace:

Thread 1 (Thread 0x7fbd89593700 (LWP 8786)):
#0  op_cancel_transfer (itransfer=0x7fbd6c000038) at os/linux_usbfs.c:2166
        tpriv = 0x7fc27c0417d8
        transfer = 0x7fbd6c000098
        __FUNCTION__ = "op_cancel_transfer"
#1  0x0000003dd0808ab6 in libusb_cancel_transfer (transfer=0x7fbd6c000098) at io.c:1494
        itransfer = 0x7fbd6c000038
        r = <optimized out>
        __FUNCTION__ = "libusb_cancel_transfer"
#2  0x00007fbd8d7c4471 in hid_close (dev=0x7fbd6c004260) at hid.c:1155
No locals.
#3  0x00007fbd8dbe8e39 in deinit_concord () from /lib64/libconcord.so.3
No symbol table info available.
#4  0x00007fbd8dbe8fc8 in reset_remote () from /lib64/libconcord.so.3
No symbol table info available.
#5  0x00007fbd8dbeb3a4 in update_configuration () from /lib64/libconcord.so.3
No symbol table info available.
#6  0x0000003db8005d8c in ffi_call_unix64 () at ../src/x86/unix64.S:76
No locals.
#7  0x0000003db80056bc in ffi_call (cif=cif@entry=0x7fbd895926b0, fn=fn@entry=0x7fbd8dbeb2c0 <update_configuration>, rvalue=rvalue@entry=0x7fbd895925c0, avalue=avalue@entry=0x7fbd89592590) at ../src/x86/ffi64.c:522
        classes = {X86_64_INTEGERSI_CLASS, 32701, 2304320960, 32701}
        stack = 0x7fbd895923a0 "\005"
        argp = 0x7fbd89592450 "\n"
        arg_types = <optimized out>
        gprcount = 3
        ssecount = <optimized out>
        ngpr = 1
        nsse = 0
        i = <optimized out>
        avn = <optimized out>
        ret_in_memory = <optimized out>
        reg_args = 0x7fbd895923a0
#8  0x00007fbd9000ac8b in _call_function_pointer (argcount=3, resmem=0x7fbd895925c0, restype=<optimized out>, atypes=<optimized out>, avalues=0x7fbd89592590, pProc=0x7fbd8dbeb2c0 <update_configuration>, flags=4353) at /usr/src/debug/Python-2.7.5/Modules/_ctypes/callproc.c:832
        error_object = 0x0
        cc = 2
        _save = 0x1c00750
        space = 0x53dfb40790adf700
        cif = {abi = FFI_UNIX64, nargs = 3, arg_types = 0x7fbd89592560, rtype = 0xdb39e0, bytes = 0, flags = 10}
#9  _ctypes_callproc (pProc=pProc@entry=0x7fbd8dbeb2c0 <update_configuration>, argtuple=argtuple@entry=0xfaf910, flags=4353, argtypes=argtypes@entry=0x18f0af0, restype=0xdb34f0, checker=0x0) at /usr/src/debug/Python-2.7.5/Modules/_ctypes/callproc.c:1179
        i = <optimized out>
        n = <optimized out>
        argcount = <optimized out>
        argtype_count = <optimized out>
        resbuf = <optimized out>
        args = 0x7fbd895925e0
        pa = <optimized out>
        atypes = <optimized out>
        rtype = <optimized out>
        avalues = <optimized out>
        retval = 0x0
#10 0x00007fbd90004a85 in PyCFuncPtr_call (self=<optimized out>, inargs=<optimized out>, kwds=<optimized out>) at /usr/src/debug/Python-2.7.5/Modules/_ctypes/_ctypes.c:3929
        restype = <optimized out>
        converters = <optimized out>
        checker = <optimized out>
        argtypes = <optimized out>
        dict = <optimized out>
        result = <optimized out>
        errcheck = <optimized out>
        pProc = <optimized out>
        inoutmask = 0
        outmask = 0
        numretvals = 0
#11 0x0000003ddbe4a0d3 in PyObject_Call () from /lib64/libpython2.7.so.1.0
No symbol table info available.
#12 0x0000003ddbede37c in PyEval_EvalFrameEx () from /lib64/libpython2.7.so.1.0
No symbol table info available.
#13 0x0000003ddbee0980 in PyEval_EvalFrameEx () from /lib64/libpython2.7.so.1.0
No symbol table info available.
#14 0x0000003ddbee21dd in PyEval_EvalCodeEx () from /lib64/libpython2.7.so.1.0
No symbol table info available.
#15 0x0000003ddbe6f0d8 in ?? () from /lib64/libpython2.7.so.1.0
No symbol table info available.
#16 0x0000003ddbe4a0d3 in PyObject_Call () from /lib64/libpython2.7.so.1.0
No symbol table info available.
#17 0x0000003ddbe590c5 in ?? () from /lib64/libpython2.7.so.1.0
No symbol table info available.
#18 0x0000003ddbe4a0d3 in PyObject_Call () from /lib64/libpython2.7.so.1.0
No symbol table info available.
#19 0x0000003ddbedc027 in PyEval_CallObjectWithKeywords () from /lib64/libpython2.7.so.1.0
No symbol table info available.
#20 0x0000003ddbf10822 in ?? () from /lib64/libpython2.7.so.1.0
No symbol table info available.
#21 0x0000003db5807ee5 in start_thread (arg=0x7fbd89593700) at pthread_create.c:309
        __res = <optimized out>
        pd = 0x7fbd89593700
        now = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {140452029871872, 3369074863727771819, 0, 0, 140452029872576, 140452029871872, -3334272243924402005, 3367057263870804139}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
        not_first_call = <optimized out>
        pagesize_m1 = <optimized out>
        sp = <optimized out>
        freesize = <optimized out>
#22 0x0000003db50f4b8d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

The full stacktrace is at https://bugzilla.redhat.com/attachment.cgi?id=956472