Index: main/dsp.c
===================================================================
--- main/dsp.c  (revision 114105)
+++ main/dsp.c  (working copy)
@@ -1495,7 +1495,12 @@
                dsp->f.subclass = AST_CONTROL_BUSY;
                ast_frfree(af);
                ast_log(LOG_DEBUG, "Requesting Hangup because the busy tone was detected on channel %s\n", chan->name);
-               return &dsp->f;
+               /* When ast_read() is called to get a frame from a channel, if we get an AST_CONTROL_BUSY frame, the reaction
+                * will be to hang up the channel and then later free the frame. The problem is that hanging up the channel
+                * will mean freeing the dsp, which means that dsp->f is now invalid memory to reference. So, instead of 
+                * passing a reference to it specifically, we duplicate the frame and pass it instead.
+                */
+               return ast_frdup(&dsp->f);
        }
        if ((dsp->features & DSP_FEATURE_DTMF_DETECT)) {
                digit = __ast_dsp_digitdetect(dsp, shortdata, len, &writeback);