Wireshark · Wireshark-dev: [Wireshark-dev] Defending against NULL dissector handles

[Neil Piercy <Neil.Piercy@xxxxxxxxxxxx>]

I've just had a bug in one of our private dissectors which meant that 
the handle passed to call_dissector was null. This seemed to give 
varying behavior - on some Windows installations it hit wireshark's 
in-built exception handling, and displayed that the dissector had an 
error (correct), but on some installations it just crashed wireshark 
(not helpful). I _think_ the difference was whether MSVC was installed 
or not, but on a sample of only 3 machines.

Should call_dissector include explicit null handle checks, and if so, 
should it:-

a) g_assert - the simple patch attached
b) fallback to doing a data decode (as disabled protocols do)
c) try to invoke the wireshark exception handling for the packet

Or is the correct answer none of the above - the exception handler 
should already cope ?

Neil

Index: packet.c
===================================================================
--- packet.c	(revision 18852)
+++ packet.c	(working copy)
@@ -1702,6 +1702,7 @@
 {
 	int ret;
 
+	g_assert(handle != NULL);
 	ret = call_dissector_work(handle, tvb, pinfo, tree);
 	if (ret == 0) {
 		/*