From 8250a7d531054d4fb0e86ca5d30429893f42d1c7 Mon Sep 17 00:00:00 2001
From: Vincent Penquerc'h <vincent.penquerch@collabora.co.uk>
Date: Thu, 17 Apr 2014 09:58:47 +0100
Subject: [PATCH] dvbbasebin: fix test for proper use count balancing

usecount is unsigned, so too many "unuse" will wrap the counter
around and the >= 0 check will always be fine.

It would be much simpler to just make the counter signed, but
moving the checks where the decrements happen allow a mistake
to be detected earlier, and thus easier to debug.

Coverity 1139791
---
 sys/dvb/dvbbasebin.c | 51 ++++++++++++++++++++++++++++++--------------
 1 file changed, 35 insertions(+), 16 deletions(-)

diff --git a/sys/dvb/dvbbasebin.c b/sys/dvb/dvbbasebin.c
index 24153fefd2..e1565ef32a 100644
--- a/sys/dvb/dvbbasebin.c
+++ b/sys/dvb/dvbbasebin.c
@@ -136,6 +136,21 @@ G_DEFINE_TYPE_EXTENDED (DvbBaseBin, dvb_base_bin, GST_TYPE_BIN,
         dvb_base_bin_uri_handler_init));
 
 
+static void
+dvb_base_bin_ref_stream (DvbBaseBinStream * stream)
+{
+  g_return_if_fail (stream != NULL);
+  stream->usecount++;
+}
+
+static void
+dvb_base_bin_unref_stream (DvbBaseBinStream * stream)
+{
+  g_return_if_fail (stream != NULL);
+  g_return_if_fail (stream->usecount > 0);
+  stream->usecount--;
+}
+
 static DvbBaseBinStream *
 dvb_base_bin_add_stream (DvbBaseBin * dvbbasebin, guint16 pid)
 {
@@ -366,7 +381,7 @@ dvb_base_bin_init (DvbBaseBin * dvbbasebin)
   i = 0;
   while (initial_pids[i] >= 0) {
     stream = dvb_base_bin_add_stream (dvbbasebin, (guint16) initial_pids[i]);
-    ++stream->usecount;
+    dvb_base_bin_ref_stream (stream);
     i++;
   }
   dvb_base_bin_rebuild_filter (dvbbasebin);
@@ -649,8 +664,6 @@ foreach_stream_build_filter (gpointer key, gpointer value, gpointer user_data)
   DvbBaseBinStream *stream = (DvbBaseBinStream *) value;
   gchar *tmp, *pid;
 
-  g_assert (stream->usecount >= 0);
-
   GST_DEBUG ("stream %d usecount %d", stream->pid, stream->usecount);
 
   if (stream->usecount > 0) {
@@ -699,7 +712,7 @@ dvb_base_bin_remove_pmt_streams (DvbBaseBin * dvbbasebin,
       continue;
     }
 
-    --stream->usecount;
+    dvb_base_bin_unref_stream (stream);
   }
 }
 
@@ -718,7 +731,7 @@ dvb_base_bin_add_pmt_streams (DvbBaseBin * dvbbasebin, const GstMpegTsPMT * pmt)
     stream = dvb_base_bin_get_stream (dvbbasebin, pmtstream->pid);
     if (stream == NULL)
       stream = dvb_base_bin_add_stream (dvbbasebin, pmtstream->pid);
-    ++stream->usecount;
+    dvb_base_bin_ref_stream (stream);
   }
 }
 
@@ -740,7 +753,7 @@ dvb_base_bin_activate_program (DvbBaseBin * dvbbasebin,
     stream = dvb_base_bin_get_stream (dvbbasebin, program->pmt_pid);
     if (stream == NULL)
       stream = dvb_base_bin_add_stream (dvbbasebin, program->pmt_pid);
-    stream->usecount += 1;
+    dvb_base_bin_ref_stream (stream);
     program->pmt_active = TRUE;
   }
 
@@ -749,13 +762,15 @@ dvb_base_bin_activate_program (DvbBaseBin * dvbbasebin,
 
     old_pcr_pid = program->pcr_pid;
     program->pcr_pid = program->pmt->pcr_pid;
-    if (old_pcr_pid != G_MAXUINT16 && old_pcr_pid != program->pcr_pid)
-      dvb_base_bin_get_stream (dvbbasebin, old_pcr_pid)->usecount--;
+    if (old_pcr_pid != G_MAXUINT16 && old_pcr_pid != program->pcr_pid) {
+      dvb_base_bin_unref_stream (dvb_base_bin_get_stream (dvbbasebin,
+              old_pcr_pid));
+    }
 
     stream = dvb_base_bin_get_stream (dvbbasebin, program->pcr_pid);
     if (stream == NULL)
       stream = dvb_base_bin_add_stream (dvbbasebin, program->pcr_pid);
-    stream->usecount += 1;
+    dvb_base_bin_ref_stream (stream);
 
     dvb_base_bin_add_pmt_streams (dvbbasebin, program->pmt);
     dvbbasebin->pmtlist =
@@ -774,12 +789,14 @@ dvb_base_bin_deactivate_program (DvbBaseBin * dvbbasebin,
   DvbBaseBinStream *stream;
 
   stream = dvb_base_bin_get_stream (dvbbasebin, program->pmt_pid);
-  if (stream != NULL)
-    stream->usecount -= 1;
+  if (stream != NULL) {
+    dvb_base_bin_unref_stream (stream);
+  }
 
   stream = dvb_base_bin_get_stream (dvbbasebin, program->pcr_pid);
-  if (stream != NULL)
-    stream->usecount -= 1;
+  if (stream != NULL) {
+    dvb_base_bin_unref_stream (stream);
+  }
 
   if (program->pmt) {
     dvb_base_bin_remove_pmt_streams (dvbbasebin, program->pmt);
@@ -851,14 +868,16 @@ dvb_base_bin_pat_info_cb (DvbBaseBin * dvbbasebin, GstMpegTsSection * section)
 
     if (program->selected) {
       /* PAT update */
-      if (old_pmt_pid != G_MAXUINT16 && old_pmt_pid != program->pmt_pid)
-        dvb_base_bin_get_stream (dvbbasebin, old_pmt_pid)->usecount -= 1;
+      if (old_pmt_pid != G_MAXUINT16 && old_pmt_pid != program->pmt_pid) {
+        dvb_base_bin_unref_stream (dvb_base_bin_get_stream (dvbbasebin,
+                old_pmt_pid));
+      }
 
       stream = dvb_base_bin_get_stream (dvbbasebin, program->pmt_pid);
       if (stream == NULL)
         stream = dvb_base_bin_add_stream (dvbbasebin, program->pmt_pid);
 
-      stream->usecount += 1;
+      dvb_base_bin_ref_stream (stream);
 
       rebuild_filter = TRUE;
     }