GVCP: Fix an infinite loop.

Remove an "if(tree)" test in order to ensure that our offset always
advances.

Bug: 16029
Change-Id: I5bb38f2eccfbf3c44a06682a17aafcba9d8fa0c6
Reviewed-on: https://code.wireshark.org/review/37611
Reviewed-by: Gerald Combs <gerald@wireshark.org>
Petri-Dish: Gerald Combs <gerald@wireshark.org>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>
(cherry picked from commit d70bd4489feed4035c3a35cd2e76cdf877b3f485)
Reviewed-on: https://code.wireshark.org/review/37618

1 files changed, 54 insertions, 57 deletions

diff --git a/epan/dissectors/packet-gvcp.c b/epan/dissectors/packet-gvcp.c
index 29622c4ce8..2de4552d43 100644
--- a/epan/dissectors/packet-gvcp.c
+++ b/epan/dissectors/packet-gvcp.c
@@ -2014,74 +2014,71 @@ static void dissect_eventdata_cmd(proto_tree *gvcp_telegram_tree, tvbuff_t *tvb,
 		/* fill in Info column in Wireshark GUI */
 		col_append_fstr(pinfo->cinfo, COL_INFO, "[ID: 0x%04X]", eventid);
 
-		if (gvcp_telegram_tree != NULL)
+		/* If extended ID, then we have event_size here (2.1) */
+		if (extendedblockids)
 		{
-			/* If extended ID, then we have event_size here (2.1) */
-			if (extendedblockids)
-			{
-				proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_extid_length, tvb, offset, 2, ENC_BIG_ENDIAN);
-				data_length = tvb_get_ntohs(tvb, offset); // We get the data length here
-			}
-
-			/* skip reserved field */
-			offset += 2;
+			proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_extid_length, tvb, offset, 2, ENC_BIG_ENDIAN);
+			data_length = tvb_get_ntohs(tvb, offset); // We get the data length here
+		}
 
-			/* Use range to determine type of event */
-			if ((eventid >= 0x0000) && (eventid <= 0x8000))
-			{
-				/* Standard ID */
-				proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_id, tvb, offset, 2, ENC_BIG_ENDIAN);
-			}
-			else if ((eventid >= 0x8001) && (eventid <= 0x8FFF))
-			{
-				/* Error */
-				proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_error_id, tvb, offset, 2, ENC_BIG_ENDIAN);
-			}
-			else if ((eventid >= 0x9000) && (eventid <= 0xFFFF))
-			{
-				/* Device specific */
-				proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_device_specific_id, tvb, offset, 2, ENC_BIG_ENDIAN);
-			}
-			offset += 2;
+		/* skip reserved field */
+		offset += 2;
 
-			/* Stream channel (possibly) associated with event */
-			proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_stream_channel_index, tvb, offset, 2, ENC_BIG_ENDIAN);
-			offset += 2;
+		/* Use range to determine type of event */
+		if ((eventid >= 0x0000) && (eventid <= 0x8000))
+		{
+			/* Standard ID */
+			proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_id, tvb, offset, 2, ENC_BIG_ENDIAN);
+		}
+		else if ((eventid >= 0x8001) && (eventid <= 0x8FFF))
+		{
+			/* Error */
+			proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_error_id, tvb, offset, 2, ENC_BIG_ENDIAN);
+		}
+		else if ((eventid >= 0x9000) && (eventid <= 0xFFFF))
+		{
+			/* Device specific */
+			proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_device_specific_id, tvb, offset, 2, ENC_BIG_ENDIAN);
+		}
+		offset += 2;
 
-			if (extendedblockids == 0)
-			{
-				/* Block id (16 bit) associated with event */
-				proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_block_id, tvb, offset, 2, ENC_BIG_ENDIAN);
-				offset += 2;
-			}
-			else
-			{
-				offset += 2;
-				/* Block id (64 bit) only if reported by gvcp flag */
-				proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_block_id_64bit_v2_0, tvb, offset, 8, ENC_BIG_ENDIAN);
-				offset += 8;
-			}
+		/* Stream channel (possibly) associated with event */
+		proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_stream_channel_index, tvb, offset, 2, ENC_BIG_ENDIAN);
+		offset += 2;
 
-			/* Timestamp (64 bit) associated with event */
-			proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_timestamp, tvb, offset, 8, ENC_BIG_ENDIAN);
+		if (extendedblockids == 0)
+		{
+			/* Block id (16 bit) associated with event */
+			proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_block_id, tvb, offset, 2, ENC_BIG_ENDIAN);
+			offset += 2;
+		}
+		else
+		{
+			offset += 2;
+			/* Block id (64 bit) only if reported by gvcp flag */
+			proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_block_id_64bit_v2_0, tvb, offset, 8, ENC_BIG_ENDIAN);
 			offset += 8;
+		}
 
-			if (extendedblockids)
-			{
-				if (data_length > 24)
-				{
-					/* Data */
-					proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_data, tvb, offset, data_length - 24, ENC_NA);
-					offset += data_length - 24;
-				}
-			}
-			else
+		/* Timestamp (64 bit) associated with event */
+		proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_timestamp, tvb, offset, 8, ENC_BIG_ENDIAN);
+		offset += 8;
+
+		if (extendedblockids)
+		{
+			if (data_length > 24)
 			{
 				/* Data */
-				proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_data, tvb, offset, -1, ENC_NA);
-				return;
+				proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_data, tvb, offset, data_length - 24, ENC_NA);
+				offset += data_length - 24;
 			}
 		}
+		else
+		{
+			/* Data */
+			proto_tree_add_item(gvcp_telegram_tree, hf_gvcp_eventcmd_data, tvb, offset, -1, ENC_NA);
+			return;
+		}
 	}
 }