criu check: don't run as non-root

In case criu check is run as non-root, a lot of information is printed
to a user, with the only missing bit is it should run it as root.

Fix it.

I still don't like the fact that some other stuff is printed here,
like the timestamp and the __FILE__:__LINE__, but this should be
fixed separately.
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-check.c

@@ -533,6 +533,9 @@ int cr_check(void)
 
 	log_set_loglevel(LOG_WARN);
 
+	if (!is_root_user())
+		return -1;
+
 	if (mntns_collect_root(getpid())) {
 		pr_err("Can't collect root mount point\n");
 		return -1;

include/util.h

@@ -272,6 +272,7 @@ extern void shfree_last(void *ptr);
 extern int run_scripts(char *action);
 
 extern int cr_system(int in, int out, int err, char *cmd, char *const argv[]);
+extern int is_root_user(void);
 
 static inline bool dir_dots(struct dirent *de)
 {

util.c

@@ -571,3 +571,13 @@ out:
 
 	return ret;
 }
+
+int is_root_user()
+{
+	if (geteuid() != 0) {
+		pr_err("You need to be root to run this command\n");
+		return 0;
+	}
+
+	return 1;
+}