[PATCH RFC] nsproxy: strengthen the comment above copy_namespaces

[Serge E. Hallyn]

copy_namespaces() cannot be used on a live task.  There are two
reasons - it can be used to assign another task's nsproxy, which
is not legal (for a live task).  And, it does not use
rcu_assign_pointer, so even when we're being extra-clever it is
unsafe.

Signed-off-by: Serge Hallyn <serue at us.ibm.com>
---
 kernel/nsproxy.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c
index f74e6c0..67d8f2b 100644
--- a/kernel/nsproxy.c
+++ b/kernel/nsproxy.c
@@ -115,6 +115,9 @@ out_ns:
 /*
  * called from clone.  This now handles copy for nsproxy and all
  * namespaces therein.
+ * Note this should only be used in fork.  Specifically, tsk should
+ * not yet be a live task.  See the the unshare code for how to handle
+ * that.
  */
 int copy_namespaces(unsigned long flags, struct task_struct *tsk)
 {
-- 
1.6.3.3