userns: Simplify the user_namespace by making userns->creator a kuid.

- Transform userns->creator from a user_struct reference to a simple
  kuid_t, kgid_t pair.

  In cap_capable this allows the check to see if we are the creator of
  a namespace to become the classic suser style euid permission check.

  This allows us to remove the need for a struct cred in the mapping
  functions and still be able to dispaly the user namespace creators
  uid and gid as 0.

- Remove the now unnecessary delayed_work in free_user_ns.

  All that is left for free_user_ns to do is to call kmem_cache_free
  and put_user_ns.  Those functions can be called in any context
  so call them directly from free_user_ns removing the need for delayed work.

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/kernel/user.c b/kernel/user.c
index 025077e54a7c..cff385659175 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -25,7 +25,8 @@ struct user_namespace init_user_ns = {
         .kref = {
                 .refcount       = ATOMIC_INIT(3),
         },
-        .creator = &root_user,
+        .owner = GLOBAL_ROOT_UID,
+        .group = GLOBAL_ROOT_GID,
 };
 EXPORT_SYMBOL_GPL(init_user_ns);
 
@@ -54,9 +55,9 @@ struct hlist_head uidhash_table[UIDHASH_SZ];
  */
 static DEFINE_SPINLOCK(uidhash_lock);
 
-/* root_user.__count is 2, 1 for init task cred, 1 for init_user_ns->user_ns */
+/* root_user.__count is 1, for init task cred */
 struct user_struct root_user = {
-        .__count        = ATOMIC_INIT(2),
+        .__count        = ATOMIC_INIT(1),
         .processes      = ATOMIC_INIT(1),
         .files          = ATOMIC_INIT(0),
         .sigpending     = ATOMIC_INIT(0),