cgroup props parser: allow empty property lists

We'll use this in the next patchset where we want to dump global properties
of the freezer cgroup, but none of the special ones for this cgroup,
because they're handled separately.
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
CC: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/cgroup-props.c

@@ -335,6 +335,11 @@ static int cgp_parse_stream(char *stream, size_t len)
 			}
 		}
 
+		if (cgp_entry->cgp.nr_props == 0 && !eat_symbol(&stream, &len, ']', true)) {
+			pr_err("Expected ']' in empty property list for %s\n", cgp_entry->cgp.name);
+			goto err_parse;
+		}
+
 		if (!eat_symbol(&stream, &len, '\n', true) && len) {
 			pr_err("Expected \'\\n\' symbol in controller's %s stream\n",
 			       cgp_entry->cgp.name);