libtraceevent: Improve error handling of tep_plugin_add_option() API

In case of memory error, ensure all allocated resources are freed.
Do not append broken option in trace_plugin_options list.

Link: https://lore.kernel.org/r/CAM9d7cizjF+fbK7YzmsBDgrx__4YAOsmEq67D3sWET8FF+YdFA@mail.gmail.com
Link: https://lore.kernel.org/linux-trace-devel/20200714103027.2477584-5-tz.stoyanov@gmail.com
Link: https://lore.kernel.org/linux-trace-devel/20200716092014.2613403-5-tz.stoyanov@gmail.com

Suggested-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: linux-trace-devel@vger.kernel.org
Link: http://lore.kernel.org/lkml/20200722011755.158091410@goodmis.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/lib/traceevent/event-plugin.c

@@ -361,23 +361,25 @@ int tep_plugin_add_option(const char *name, const char *val)
 	if (!op) {
 		op = malloc(sizeof(*op));
 		if (!op)
-			return -ENOMEM;
+			goto out_free;
 		memset(op, 0, sizeof(*op));
-		op->next = trace_plugin_options;
-		trace_plugin_options = op;
-
 		op->plugin = plugin;
 		op->option = option_str;
-
 		if (val) {
 			op->value = strdup(val);
-			if (!op->value)
+			if (!op->value) {
+				free(op);
 				goto out_free;
+			}
 		}
+		op->next = trace_plugin_options;
+		trace_plugin_options = op;
 	}
 
 	return process_option(plugin, option_str, val);
- out_free:
+
+out_free:
+	free(plugin);
 	free(option_str);
 	return -ENOMEM;
 }