kafka: zstd: free the composite tvb only once

Fix the composite tvb handling for zstd decompression in the same way as
we already did for lz4 and snappy.

Allocate the composite tvb only if we are cetain that data will be added
to it. Do not free the composite tvb ourselves, leave this to epan cleanup.

Change-Id: Iac74ea6e6d220b05858a7eb267276ff983b1b2ab
Reviewed-on: https://code.wireshark.org/review/37900
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>
Petri-Dish: Martin Kaiser <wireshark@kaiser.cx>
Tested-by: Petri Dish Buildbot
Reviewed-by: Alexis La Goutte <alexis.lagoutte@gmail.com>

1 files changed, 11 insertions, 8 deletions

diff --git a/epan/dissectors/packet-kafka.c b/epan/dissectors/packet-kafka.c
index dc43b9f172..98404d951d 100644
--- a/epan/dissectors/packet-kafka.c
+++ b/epan/dissectors/packet-kafka.c
@@ -1504,7 +1504,7 @@ decompress_zstd(tvbuff_t *tvb, packet_info *pinfo, int offset, guint32 length, t
     ZSTD_inBuffer input = { tvb_memdup(wmem_packet_scope(), tvb, offset, length), length, 0 };
     ZSTD_DStream *zds = ZSTD_createDStream();
     size_t rc = 0;
-    tvbuff_t *composite_tvb = tvb_new_composite();
+    tvbuff_t *composite_tvb = NULL;
     int ret = 0;
 
     do {
@@ -1515,21 +1515,24 @@ decompress_zstd(tvbuff_t *tvb, packet_info *pinfo, int offset, guint32 length, t
         if (ZSTD_isError(rc)) {
             goto end;
         }
+        if (!composite_tvb) {
+            composite_tvb = tvb_new_composite();
+        }
         tvb_composite_append(composite_tvb,
                              tvb_new_child_real_data(tvb, (guint8*)output.dst, (guint)output.pos, (gint)output.pos));
         // rc == 0 means there is nothing more to decompress, but there could be still something in the data
     } while (rc > 0);
-    tvb_composite_finalize(composite_tvb);
-    *decompressed_tvb = composite_tvb;
-    *decompressed_offset = 0;
-    composite_tvb = NULL;
     ret = 1;
 end:
+    if (composite_tvb) {
+        tvb_composite_finalize(composite_tvb);
+    }
     ZSTD_freeDStream(zds);
-    if (composite_tvb != NULL) {
-        tvb_free_chain(composite_tvb);
+    if (ret == 1) {
+        *decompressed_tvb = composite_tvb;
+        *decompressed_offset = 0;
     }
-    if (ret == 0) {
+    else {
         col_append_str(pinfo->cinfo, COL_INFO, " [zstd decompression failed]");
     }
     return ret;