unirec: BUGFIX possible NULL pointer dereference

In case the pointer to configuration is NULL it is not possible to free
any member of that structure.

Checks were added and some lines were reordered.

Author: cejkato2

extra_plugins/output/unirec/unirecplugin.c

@@ -237,8 +237,10 @@ ipx_plugin_init(ipx_ctx_t *ctx, const char *params)
     free(cleaned_urtemplate);
     ipx_plugin_destroy(ctx, conf);
     free_IPFIX2UR_map(map);
-    free(conf->ur_message);
-    free(conf);
+    if (conf != NULL) {
+        free(conf->ur_message);
+        free(conf);
+    }
     return IPX_ERR_DENIED;
 }
 
@@ -293,26 +295,8 @@ ipx_plugin_destroy(ipx_ctx_t *ctx, void *cfg)
 {
     (void) ctx;
     struct conf_unirec *conf = (struct conf_unirec *) cfg;
-    if (conf == NULL) {
-        IPX_CTX_ERROR(ctx, "configuration is NULL! Skipping ipx_plugin_destroy()");
-    }
-
     IPX_CTX_INFO(ctx, "UniRec plugin finalization.");
 
-    trap_ctx_terminate(conf->tctx);
-
-    // Destroy a translator and a record
-    translator_destroy(conf->translator);
-
-    // Destroy parsed XML configuration
-    configuration_free(conf->params);
-
-    trap_ctx_finalize(&conf->tctx);
-
-    ur_free_template(conf->urtmpl);
-
-    free(conf->ur_message);
-
     if (pthread_mutex_lock(&urp_mutex) == -1) {
         IPX_CTX_ERROR(ctx, "Could not lock. (%s:%d)", __FILE__, __LINE__);
     }
@@ -324,7 +308,23 @@ ipx_plugin_destroy(ipx_ctx_t *ctx, void *cfg)
     if (pthread_mutex_unlock(&urp_mutex) == -1) {
         IPX_CTX_ERROR(ctx, "Could not unlock. (%s:%d)", __FILE__, __LINE__);
     }
-    // Destroy instance structure
-    free(conf);
+
+    if (conf != NULL) {
+        trap_ctx_terminate(conf->tctx);
+        // Destroy a translator and a record
+        translator_destroy(conf->translator);
+
+        // Destroy parsed XML configuration
+        configuration_free(conf->params);
+
+        trap_ctx_finalize(&conf->tctx);
+
+        ur_free_template(conf->urtmpl);
+
+        free(conf->ur_message);
+
+        // Destroy instance structure
+        free(conf);
+    }
 }