[Bug 660357] New: [gst-python] Fix decref of null pointer

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=660357
  GStreamer | gst-python | git

           Summary: [gst-python] Fix decref of null pointer
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-python
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: ylatuya at gmail.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Created an attachment (id=197661)
 View: https://bugzilla.gnome.org/attachment.cgi?id=197661
 Review: https://bugzilla.gnome.org/review?bug=660357&attachment=197661

Fix decref of null pointer

I caught a segfault in gst-python that I can't reproduce, but I have a
coredump. It's seems that if the call to the callback fails, args can be NULL.
Attached patch.


(gdb) frame 0
#0  pad_block_callback_marshal (pad=0x8ac21a0, blocked=1, user_data=0xb778a4ec)
at gstpad.override:1393
1393        Py_DECREF(args);
(gdb) bt
#0  pad_block_callback_marshal (pad=0x8ac21a0, blocked=1, user_data=0xb778a4ec)
at gstpad.override:1393
#1  0x0096a8b2 in handle_pad_block (pad=0x8ac21a0) at gstpad.c:4000
#2  0x009766c8 in gst_pad_push_event (pad=0x8ac21a0, event=0x8b48600) at
gstpad.c:4951
#3  0x00814aca in gst_base_src_loop (pad=0x8ac21a0) at gstbasesrc.c:2403
#4  0x0099e5b4 in gst_task_func (task=0x8c92250) at gsttask.c:271
#5  0x0099fef7 in default_func (tdata=0x8d82d00, pool=0x874e008) at
gsttaskpool.c:70
#6  0x06fa0968 in g_thread_pool_push () from /lib/libglib-2.0.so.0
#7  0x06f9ee7f in g_thread_create_full () from /lib/libglib-2.0.so.0
#8  0x005c945b in start_thread () from /lib/libpthread.so.0
#9  0x00520c4e in clone () from /lib/libc.so.6
(gdb) l
1381        callback = PyTuple_GetItem(py_user_data, 0);
1382        args = Py_BuildValue("(NO)",
1383                 pygobject_new(G_OBJECT(pad)),
1384                 blocked ? Py_True : Py_False);
1385        
1386        {
1387            PyObject *tmp = args;
1388            args = PySequence_Concat(tmp, PyTuple_GetItem(py_user_data,
1));
1389            Py_DECREF (tmp);
1390        }
1391    
1392        ret = PyObject_CallObject(callback, args);
1393        Py_DECREF(args);
1394    
1395        if (!ret)
1396            PyErr_Print();
1397        else
1398            Py_DECREF(ret);
1399        
1400        pyg_gil_state_release(state);
1401    }
1402    
1403    static PyObject *
1404    _wrap_gst_pad_set_blocked_async (PyGObject *self, PyObject *args)
1405    {
(gdb) print *args
Cannot access memory at address 0x0
(gdb) print *ret
Cannot access memory at address 0x0
(gdb)

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