2.6.26-rc1

 kernel

diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index f5d332c..adc7851 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -139,6 +139,18 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk)
       goto out;
    }
 
+   /*
+    * CLONE_NEWIPC must detach from the undolist: after switching
+    * to a new ipc namespace, the semaphore arrays from the old
+    * namespace are unreachable.  In clone parlance, CLONE_SYSVSEM
+    * means share undolist with parent, so we must forbid using
+    * it along with CLONE_NEWIPC.
+    */
+   if ((flags & CLONE_NEWIPC) && (flags & CLONE_SYSVSEM)) {
+      err = -EINVAL;
+      goto out;
+   }
+
    new_ns = create_new_namespaces(flags, tsk, tsk->fs);
    if (IS_ERR(new_ns)) {
       err = PTR_ERR(new_ns);