python: Fix python plugin crash

If python pugin reads and writes collectd values, the write python
plugin callback may crash (90%) on free table var (line 478) if the
meta data structure is created but no information is present there.
It's possible to reproduce it due to changes introduced by #2135 PR.

cpy_write_callback():
 ...
 425   if (value_list->meta) {
 426     char **table;
 427     meta_data_t *meta = value_list->meta;
 428
 429     int num = meta_data_toc(meta, &table);
 430     for (int i = 0; i < num; ++i) {
 ...
 477     }
 478     free(table);
 479   }

Change-Id: Ic897933f447b9280f266b6e78b6b73bd12182eba
Signed-off-by: Mytnyk, VolodymyrX <volodymyrx.mytnyk@intel.com>

diff --git a/src/python.c b/src/python.c
index d4efa94..a8f5177 100644 (file)
--- a/src/python.c
+++ b/src/python.c
@@ -423,7 +423,7 @@ static int cpy_write_callback(const data_set_t *ds,
   }
   dict = PyDict_New(); /* New reference. */
   if (value_list->meta) {
-    char **table;
+    char **table = NULL;
     meta_data_t *meta = value_list->meta;
 
     int num = meta_data_toc(meta, &table);

diff --git a/src/pyvalues.c b/src/pyvalues.c
index 9c8809d..5dcdf6a 100644 (file)
--- a/src/pyvalues.c
+++ b/src/pyvalues.c
@@ -576,7 +576,10 @@ CPY_BUILD_META_HANDLER(plugin_notification_meta, notification_t);
 
 static meta_data_t *cpy_build_value_meta(PyObject *meta) {
   meta_data_t *m = meta_data_create();
-  cpy_build_meta(meta, &cpy_meta_data, (void *)m);
+  if (cpy_build_meta(meta, &cpy_meta_data, (void *)m) < 0) {
+    meta_data_destroy(m);
+    return NULL;
+  }
   return m;
 }