[RFC][PATCH] Deny CLONE_PARENT|CLONE_NEWPID|CLONE_SIGHAND combination

[Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>]

Deny CLONE_PARENT|CLONE_NEWPID|CLONE_SIGHAND combination.

CLONE_PARENT was used to implement an older threading model.  For consistency
with the CLONE_THREAD check in copy_pid_ns(), disable CLONE_PARENT and
CLONE_SIGHAND with CLONE_NEWPID, at least until the required semantics of
the pid namespaces are clear.

Changelog[v2]:
	[Eric Biederman] Disable CLONE_SIGHAND also ???

Signed-off-by: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Acked-by: Roland McGrath <roland@redhat.com>
---
 kernel/pid_namespace.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-mmotm/kernel/pid_namespace.c
===================================================================
--- linux-mmotm.orig/kernel/pid_namespace.c	2009-06-30 23:01:09.000000000 -0700
+++ linux-mmotm/kernel/pid_namespace.c	2009-06-30 23:49:06.000000000 -0700
@@ -118,7 +118,7 @@ struct pid_namespace *copy_pid_ns(unsign
 {
 	if (!(flags & CLONE_NEWPID))
 		return get_pid_ns(old_ns);
-	if (flags & CLONE_THREAD)
+	if (flags & (CLONE_THREAD|CLONE_PARENT|CLONE_SIGHAND))
 		return ERR_PTR(-EINVAL);
 	return create_pid_namespace(old_ns);
 }