1 files changed, 76 insertions, 0 deletions
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
new file mode 100644
index 0000000..532858f
--- /dev/null
+++ b/kernel/user_namespace.c
@@ -0,0 +1,76 @@
+/*
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License as
+ *  published by the Free Software Foundation, version 2 of the
+ *  License.
+ */
+
+#include <linux/module.h>
+#include <linux/nsproxy.h>
+#include <linux/slab.h>
+#include <linux/user_namespace.h>
+
+/*
+ * Clone a new ns copying an original user ns, setting refcount to 1
+ * @old_ns: namespace to clone
+ * Return NULL on error (failure to kmalloc), new ns otherwise
+ */
+static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
+{
+	struct user_namespace *ns;
+	struct user_struct *new_user;
+	int n;
+
+	ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
+	if (!ns)
+		return ERR_PTR(-ENOMEM);
+
+	kref_init(&ns->kref);
+
+	for (n = 0; n < UIDHASH_SZ; ++n)
+		INIT_HLIST_HEAD(ns->uidhash_table + n);
+
+	/* Insert new root user.  */
+	ns->root_user = alloc_uid(ns, 0);
+	if (!ns->root_user) {
+		kfree(ns);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	/* Reset current->user with a new one */
+	new_user = alloc_uid(ns, current->uid);
+	if (!new_user) {
+		free_uid(ns->root_user);
+		kfree(ns);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	switch_uid(new_user);
+	return ns;
+}
+
+struct user_namespace * copy_user_ns(int flags, struct user_namespace *old_ns)
+{
+	struct user_namespace *new_ns;
+
+	BUG_ON(!old_ns);
+	get_user_ns(old_ns);
+
+	if (!(flags & CLONE_NEWUSER))
+		return old_ns;
+
+	new_ns = clone_user_ns(old_ns);
+
+	put_user_ns(old_ns);
+	return new_ns;
+}
+
+void free_user_ns(struct kref *kref)
+{
+	struct user_namespace *ns;
+
+	ns = container_of(kref, struct user_namespace, kref);
+	release_uids(ns);
+	kfree(ns);
+}
+EXPORT_SYMBOL(free_user_ns);