Add a debug helper for EP memory corruption

if compiled in and the env var WIRESHARK_DEBUG_EP_CANARY is set:
will check for canary integrity at every call to EP_CHECK_CANARY()
if corruption is found it exits pronting the prior location and the location in which corruption was found.
Hopefully it stops running while the corruptor is still in the stack.

see EP_CHECK_CANARY() calls in packet.c as an example.




svn path=/trunk/; revision=25927

1 files changed, 17 insertions, 2 deletions

diff --git a/epan/packet.c b/epan/packet.c
index 07c93b2cb7..dbf6953ab4 100644
--- a/epan/packet.c
+++ b/epan/packet.c
@@ -51,6 +51,7 @@
 #include "tvbuff.h"
 #include "plugins.h"
 #include "epan_dissect.h"
+
 #include "emem.h"
 
 #include <epan/reassemble.h>
@@ -320,6 +321,8 @@ dissect_packet(epan_dissect_t *edt, union wtap_pseudo_header *pseudo_header,
 	edt->pi.clnp_srcref = 0;
 	edt->pi.clnp_dstref = 0;
 
+    EP_CHECK_CANARY(("before dissecting frame %d",fd->num));
+    
 	TRY {
 		edt->tvb = tvb_new_real_data(pd, fd->cap_len, fd->pkt_len);
 		/* Add this tvbuffer into the data_src list */
@@ -348,6 +351,8 @@ dissect_packet(epan_dissect_t *edt, union wtap_pseudo_header *pseudo_header,
 		RETHROW;
 	}
 	ENDTRY;
+    
+    EP_CHECK_CANARY(("after dissecting frame %d",fd->num));
 
 	fd->flags.visited = 1;
 }
@@ -392,9 +397,13 @@ call_dissector_through_handle(dissector_handle_t handle, tvbuff_t *tvb,
 	}
 
 	if (handle->is_new) {
+        EP_CHECK_CANARY(("before calling handle->dissector.new for %s",handle->name));
 		ret = (*handle->dissector.new)(tvb, pinfo, tree);
+        EP_CHECK_CANARY(("after calling handle->dissector.new for %s",handle->name));
 	} else {
+        EP_CHECK_CANARY(("before calling handle->dissector.old for %s",handle->name));
 		(*handle->dissector.old)(tvb, pinfo, tree);
+        EP_CHECK_CANARY(("after calling handle->dissector.old for %s",handle->name));
 		ret = tvb_length(tvb);
 		if (ret == 0) {
 			/*
@@ -1592,11 +1601,17 @@ dissector_try_heuristic(heur_dissector_list_t sub_dissectors,
 					proto_get_protocol_filter_name(proto_get_id(dtbl_entry->protocol)));
 			}
 		}
-
+        EP_CHECK_CANARY(("before calling heuristic dissector for protocol: %s",
+                         proto_get_protocol_filter_name(proto_get_id(dtbl_entry->protocol))));
 		if ((*dtbl_entry->dissector)(tvb, pinfo, tree)) {
+            EP_CHECK_CANARY(("after heuristic dissector for protocol: %s has accepted and dissected packet",
+                             proto_get_protocol_filter_name(proto_get_id(dtbl_entry->protocol))));
 			status = TRUE;
 			break;
 		} else {
+            EP_CHECK_CANARY(("after heuristic dissector for protocol: %s has returned true",
+                             proto_get_protocol_filter_name(proto_get_id(dtbl_entry->protocol))));
+
 			/*
 			 * That dissector didn't accept the packet, so
 			 * remove its protocol's name from the list
@@ -1605,7 +1620,7 @@ dissector_try_heuristic(heur_dissector_list_t sub_dissectors,
 			if (pinfo->layer_names != NULL) {
 				g_string_truncate(pinfo->layer_names,
 				    saved_layer_names_len);
-			}
+            }
 		}
 	}
 	pinfo->current_proto = saved_proto;