1 files changed, 87 insertions, 0 deletions

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
new file mode 100644
index 000000000000..d055d987850c
--- /dev/null
+++ b/kernel/user_namespace.c
@@ -0,0 +1,87 @@
+/*
+ *  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/version.h>
+#include <linux/nsproxy.h>
+#include <linux/user_namespace.h>
+
+struct user_namespace init_user_ns = {
+        .kref = {
+                .refcount       = ATOMIC_INIT(2),
+        },
+        .root_user = &root_user,
+};
+
+EXPORT_SYMBOL_GPL(init_user_ns);
+
+#ifdef CONFIG_USER_NS
+
+/*
+ * 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_LIST_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);
+        kfree(ns);
+}
+
+#endif /* CONFIG_USER_NS */