1 files changed, 45 insertions, 1 deletions

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 3d7964209774..89a27e8b17fb 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -21,6 +21,45 @@ 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 NULL;
+
+        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 NULL;
+        }
+
+        /* 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 NULL;
+        }
+
+        switch_uid(new_user);
+        return ns;
+}
+
 struct user_namespace * copy_user_ns(int flags, struct user_namespace *old_ns)
 {
         struct user_namespace *new_ns;
@@ -28,7 +67,12 @@ struct user_namespace * copy_user_ns(int flags, struct user_namespace *old_ns)
         BUG_ON(!old_ns);
         get_user_ns(old_ns);
 
-        new_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;
 }