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DVB-S2: Only create composite if used 

It violates the tvb_composite API to create composite TVBs if
they're not going to have at least one TVB put in them. Prevent
dissector bug failed assertions in the case of packets incorrectly
identified as DVB Baseband frames carrying TS by the heuristic
dissector.
This commit is contained in:
John Thacker 2021-08-31 08:42:52 -04:00 committed by Wireshark GitLab Utility
parent 033068916d
commit b04165a57b
1 changed files with 9 additions and 4 deletions
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13
epan/dissectors/packet-dvb-s2-bb.c
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@ -1474,7 +1474,7 @@ static int dissect_dvb_s2_bb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree
fragment_head *fd_head;
dvbs2_bb_data *pdata;
gboolean npd;
gboolean npd, composite_init = FALSE;
guint8 input8, matype1, crc8, isi = 0, issyi;
guint8 sync_flag = 0;
guint16 input16, bb_data_len = 0, user_packet_length, syncd;
@ -1797,7 +1797,6 @@ static int dissect_dvb_s2_bb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree
}
if (dvb_s2_df_dissection && user_packet_length) {
sync_tvb = tvb_new_subset_length(tvb, DVB_S2_BB_OFFS_SYNC, 1);
tsp_tvb = tvb_new_composite();
ts_stream = find_stream(subcircuit, pinfo->p2p_dir);
if (ts_stream == NULL) {
ts_stream = stream_new(subcircuit, pinfo->p2p_dir);
@ -1835,6 +1834,8 @@ static int dissect_dvb_s2_bb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree
"Reassembled TSP", ts_frag, &dvbs2_frag_items, NULL,
tree);
if (next_tvb && tvb_reported_length(next_tvb) == user_packet_length) {
tsp_tvb = tvb_new_composite();
composite_init = TRUE;
tvb_composite_append(tsp_tvb, sync_tvb);
proto_tree_add_checksum(dvb_s2_bb_tree, next_tvb, 0,
hf_dvb_s2_bb_up_crc, hf_dvb_s2_bb_up_crc_status,
@ -1867,6 +1868,10 @@ static int dissect_dvb_s2_bb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree
proto_tree_add_checksum(dvb_s2_bb_tree, tvb, new_off,
hf_dvb_s2_bb_up_crc, hf_dvb_s2_bb_up_crc_status,
&ei_dvb_s2_bb_crc, pinfo, crc8, ENC_NA, flags);
if (!composite_init) {
tsp_tvb = tvb_new_composite();
composite_init = TRUE;
}
tvb_composite_append(tsp_tvb, sync_tvb);
new_off++;
crc8 = compute_crc8(tvb, user_packet_length - 1, new_off);
@ -1897,8 +1902,8 @@ static int dissect_dvb_s2_bb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree
next_tvb = stream_process_reassembled(next_tvb, 0, pinfo,
"Reassembled TSP", ts_frag, &dvbs2_frag_items, NULL, tree);
}
tvb_composite_finalize(tsp_tvb);
if (tvb_reported_length(tsp_tvb)) {
if (composite_init) {
tvb_composite_finalize(tsp_tvb);
add_new_data_source(pinfo, tsp_tvb, "Sync-swapped TS");
/* The way the MP2T dissector handles reassembly (using the
* offsets into the TVB to store per-packet information), it