ns: add ns_debug()

Add ns_debug() that asserts that the correct operations are used for the
namespace type.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: brauner

kernel/nscommon.c

@@ -2,6 +2,55 @@
 
 #include <linux/ns_common.h>
 #include <linux/proc_ns.h>
+#include <linux/vfsdebug.h>
+
+#ifdef CONFIG_DEBUG_VFS
+static void ns_debug(struct ns_common *ns, const struct proc_ns_operations *ops)
+{
+	switch (ns->ops->type) {
+#ifdef CONFIG_CGROUPS
+	case CLONE_NEWCGROUP:
+		VFS_WARN_ON_ONCE(ops != &cgroupns_operations);
+		break;
+#endif
+#ifdef CONFIG_IPC_NS
+	case CLONE_NEWIPC:
+		VFS_WARN_ON_ONCE(ops != &ipcns_operations);
+		break;
+#endif
+	case CLONE_NEWNS:
+		VFS_WARN_ON_ONCE(ops != &mntns_operations);
+		break;
+#ifdef CONFIG_NET_NS
+	case CLONE_NEWNET:
+		VFS_WARN_ON_ONCE(ops != &netns_operations);
+		break;
+#endif
+#ifdef CONFIG_PID_NS
+	case CLONE_NEWPID:
+		VFS_WARN_ON_ONCE(ops != &pidns_operations);
+		break;
+#endif
+#ifdef CONFIG_TIME_NS
+	case CLONE_NEWTIME:
+		VFS_WARN_ON_ONCE(ops != &timens_operations);
+		break;
+#endif
+#ifdef CONFIG_USER_NS
+	case CLONE_NEWUSER:
+		VFS_WARN_ON_ONCE(ops != &userns_operations);
+		break;
+#endif
+#ifdef CONFIG_UTS_NS
+	case CLONE_NEWUTS:
+		VFS_WARN_ON_ONCE(ops != &utsns_operations);
+		break;
+#endif
+	default:
+		VFS_WARN_ON_ONCE(true);
+	}
+}
+#endif
 
 int __ns_common_init(struct ns_common *ns, const struct proc_ns_operations *ops, int inum)
 {
@@ -12,6 +61,10 @@ int __ns_common_init(struct ns_common *ns, const struct proc_ns_operations *ops,
 	RB_CLEAR_NODE(&ns->ns_tree_node);
 	INIT_LIST_HEAD(&ns->ns_list_node);
 
+#ifdef CONFIG_DEBUG_VFS
+	ns_debug(ns, ops);
+#endif
+
 	if (inum) {
 		ns->inum = inum;
 		return 0;