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, 5 insertions, 3 deletions

diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index f084083a0fd3..58bb8781a778 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -24,7 +24,7 @@ static struct kmem_cache *user_ns_cachep __read_mostly;
  */
 int create_user_ns(struct cred *new)
 {
-        struct user_namespace *ns;
+        struct user_namespace *ns, *parent_ns = new->user_ns;
         struct user_struct *root_user;
         int n;
 
@@ -57,8 +57,10 @@ int create_user_ns(struct cred *new)
 #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);
+        /* Leave the reference to our user_ns with the new cred */
+        new->user_ns = ns;
+
+        put_user_ns(parent_ns);
 
         return 0;
 }