ucount: Make sure ucounts in /proc/sys/user don't regress again

Commit 769071ac9f "ns: Introduce Time Namespace" broke reporting of
inotify ucounts (max_inotify_instances, max_inotify_watches) in
/proc/sys/user because it has added UCOUNT_TIME_NAMESPACES into enum
ucount_type but didn't properly update reporting in
kernel/ucount.c:setup_userns_sysctls(). This problem got fixed in commit
eeec26d5da "time/namespace: Add max_time_namespaces ucount".

Add BUILD_BUG_ON to catch a similar problem in the future.

Signed-off-by: Jan Kara <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Andrei Vagin <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]

kernel/ucount.c

@@ -82,6 +82,8 @@ bool setup_userns_sysctls(struct user_namespace *ns)
 {
 #ifdef CONFIG_SYSCTL
 	struct ctl_table *tbl;
+
+	BUILD_BUG_ON(ARRAY_SIZE(user_table) != UCOUNT_COUNTS + 1);
 	setup_sysctl_set(&ns->set, &set_root, set_is_seen);
 	tbl = kmemdup(user_table, sizeof(user_table), GFP_KERNEL);
 	if (tbl) {