UBUNTU: Ubuntu-2.6.38-12.51

[linux-flexiantxendom0-natty.git] / kernel / user_namespace.c

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index 2731ba8..9da289c 100644 (file)
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -6,71 +6,132 @@
  */
 
 #include <linux/module.h>
-#include <linux/version.h>
 #include <linux/nsproxy.h>
 #include <linux/slab.h>
 #include <linux/user_namespace.h>
+#include <linux/highuid.h>
+#include <linux/cred.h>
+
+static struct kmem_cache *user_ns_cachep __read_mostly;
 
 /*
- * 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
+ * Create a new user namespace, deriving the creator from the user in the
+ * passed credentials, and replacing that user with the new root user for the
+ * new namespace.
+ *
+ * This is called by copy_creds(), which will finish setting the target task's
+ * credentials.
  */
-static struct user_namespace *clone_user_ns(struct user_namespace *old_ns)
+int create_user_ns(struct cred *new)
 {
        struct user_namespace *ns;
-       struct user_struct *new_user;
+       struct user_struct *root_user;
        int n;
 
-       ns = kmalloc(sizeof(struct user_namespace), GFP_KERNEL);
+       ns = kmem_cache_alloc(user_ns_cachep, GFP_KERNEL);
        if (!ns)
-               return ERR_PTR(-ENOMEM);
+               return -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);
+       /* Alloc new root user.  */
+       root_user = alloc_uid(ns, 0);
+       if (!root_user) {
+               kmem_cache_free(user_ns_cachep, ns);
+               return -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);
-       }
+       /* set the new root user in the credentials under preparation */
+       ns->creator = new->user;
+       new->user = root_user;
+       new->uid = new->euid = new->suid = new->fsuid = 0;
+       new->gid = new->egid = new->sgid = new->fsgid = 0;
+       put_group_info(new->group_info);
+       new->group_info = get_group_info(&init_groups);
+#ifdef CONFIG_KEYS
+       key_put(new->request_key_auth);
+       new->request_key_auth = NULL;
+#endif
+       /* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
+
+       /* root_user holds a reference to ns, our reference can be dropped */
+       put_user_ns(ns);
+
+       return 0;
+}
+
+/*
+ * Deferred destructor for a user namespace.  This is required because
+ * free_user_ns() may be called with uidhash_lock held, but we need to call
+ * back to free_uid() which will want to take the lock again.
+ */
+static void free_user_ns_work(struct work_struct *work)
+{
+       struct user_namespace *ns =
+               container_of(work, struct user_namespace, destroyer);
+       free_uid(ns->creator);
+       kmem_cache_free(user_ns_cachep, ns);
+}
+
+void free_user_ns(struct kref *kref)
+{
+       struct user_namespace *ns =
+               container_of(kref, struct user_namespace, kref);
 
-       switch_uid(new_user);
-       return ns;
+       INIT_WORK(&ns->destroyer, free_user_ns_work);
+       schedule_work(&ns->destroyer);
 }
+EXPORT_SYMBOL(free_user_ns);
 
-struct user_namespace * copy_user_ns(int flags, struct user_namespace *old_ns)
+uid_t user_ns_map_uid(struct user_namespace *to, const struct cred *cred, uid_t uid)
 {
-       struct user_namespace *new_ns;
+       struct user_namespace *tmp;
 
-       BUG_ON(!old_ns);
-       get_user_ns(old_ns);
+       if (likely(to == cred->user->user_ns))
+               return uid;
 
-       if (!(flags & CLONE_NEWUSER))
-               return old_ns;
 
-       new_ns = clone_user_ns(old_ns);
+       /* Is cred->user the creator of the target user_ns
+        * or the creator of one of it's parents?
+        */
+       for ( tmp = to; tmp != &init_user_ns;
+             tmp = tmp->creator->user_ns ) {
+               if (cred->user == tmp->creator) {
+                       return (uid_t)0;
+               }
+       }
 
-       put_user_ns(old_ns);
-       return new_ns;
+       /* No useful relationship so no mapping */
+       return overflowuid;
 }
 
-void free_user_ns(struct kref *kref)
+gid_t user_ns_map_gid(struct user_namespace *to, const struct cred *cred, gid_t gid)
 {
-       struct user_namespace *ns;
+       struct user_namespace *tmp;
+
+       if (likely(to == cred->user->user_ns))
+               return gid;
 
-       ns = container_of(kref, struct user_namespace, kref);
-       release_uids(ns);
-       kfree(ns);
+       /* Is cred->user the creator of the target user_ns
+        * or the creator of one of it's parents?
+        */
+       for ( tmp = to; tmp != &init_user_ns;
+             tmp = tmp->creator->user_ns ) {
+               if (cred->user == tmp->creator) {
+                       return (gid_t)0;
+               }
+       }
+
+       /* No useful relationship so no mapping */
+       return overflowgid;
+}
+
+static __init int user_namespaces_init(void)
+{
+       user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
+       return 0;
 }
+module_init(user_namespaces_init);