1 files changed, 26 insertions, 0 deletions

diff --git a/ipc/namespace.c b/ipc/namespace.c
index 1b967655eb35..9171d948751e 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -20,10 +20,20 @@ static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
         if (ns == NULL)
                 return ERR_PTR(-ENOMEM);
 
+        atomic_inc(&nr_ipc_ns);
+
         sem_init_ns(ns);
         msg_init_ns(ns);
         shm_init_ns(ns);
 
+        /*
+         * msgmni has already been computed for the new ipc ns.
+         * Thus, do the ipcns creation notification before registering that
+         * new ipcns in the chain.
+         */
+        ipcns_notify(IPCNS_CREATED);
+        register_ipcns_notifier(ns);
+
         kref_init(&ns->kref);
         return ns;
 }
@@ -79,8 +89,24 @@ void free_ipc_ns(struct kref *kref)
         struct ipc_namespace *ns;
 
         ns = container_of(kref, struct ipc_namespace, kref);
+        /*
+         * Unregistering the hotplug notifier at the beginning guarantees
+         * that the ipc namespace won't be freed while we are inside the
+         * callback routine. Since the blocking_notifier_chain_XXX routines
+         * hold a rw lock on the notifier list, unregister_ipcns_notifier()
+         * won't take the rw lock before blocking_notifier_call_chain() has
+         * released the rd lock.
+         */
+        unregister_ipcns_notifier(ns);
         sem_exit_ns(ns);
         msg_exit_ns(ns);
         shm_exit_ns(ns);
         kfree(ns);
+        atomic_dec(&nr_ipc_ns);
+
+        /*
+         * Do the ipcns removal notification after decrementing nr_ipc_ns in
+         * order to have a correct value when recomputing msgmni.
+         */
+        ipcns_notify(IPCNS_REMOVED);
 }