cred: Refcount the user_ns pointed to by the cred.

struct user_struct will shortly loose it's user_ns reference
so make the cred user_ns reference a proper reference complete
with reference counting.

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

1 files changed, 3 insertions, 5 deletions

diff --git a/kernel/cred.c b/kernel/cred.c
index 97b36eeca4c9..7a0d80669886 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -148,6 +148,7 @@ static void put_cred_rcu(struct rcu_head *rcu)
         if (cred->group_info)
                 put_group_info(cred->group_info);
         free_uid(cred->user);
+        put_user_ns(cred->user_ns);
         kmem_cache_free(cred_jar, cred);
 }
 
@@ -303,6 +304,7 @@ struct cred *prepare_creds(void)
         set_cred_subscribers(new, 0);
         get_group_info(new->group_info);
         get_uid(new->user);
+        get_user_ns(new->user_ns);
 
 #ifdef CONFIG_KEYS
         key_get(new->thread_keyring);
@@ -412,11 +414,6 @@ int copy_creds(struct task_struct *p, unsigned long clone_flags)
                         goto error_put;
         }
 
-        /* cache user_ns in cred.  Doesn't need a refcount because it will
-         * stay pinned by cred->user
-         */
-        new->user_ns = new->user->user_ns;
-
 #ifdef CONFIG_KEYS
         /* new threads get their own thread keyrings if their parent already
          * had one */
@@ -676,6 +673,7 @@ struct cred *prepare_kernel_cred(struct task_struct *daemon)
         atomic_set(&new->usage, 1);
         set_cred_subscribers(new, 0);
         get_uid(new->user);
+        get_user_ns(new->user_ns);
         get_group_info(new->group_info);
 
 #ifdef CONFIG_KEYS