I've attached a new version of the patch.
The patch is now split into 2 parts:

* add copy_user_to_user() into kernel/ptrace.c. Most code is shared
between access_process_vm() and copy_user_to_user().

* use the new function for singlecopy pipe.

Please test it.
The kernel space part should be ok, but I know that the
patch can cause deadlocks with buggy user space apps.

--
	Manfred