There is a small window where it's possible that we could be working
on an interrupt (queued in the workqueue) and setting up a channel
program (i.e allocating memory, pinning pages, translating address).
This can lead to allocating and freeing the channel program at the
same time and can cause memory corruption.

Let's not call cp_free if we are currently processing a channel program.
The only way we know for sure that we don't have a thread setting
up a channel program is when the state is set to VFIO_CCW_STATE_CP_PENDING.

Fixes: d5afd5d1 ("vfio-ccw: add handling for async channel instructions")
Signed-off-by: NFarhan Ali <alifm@linux.ibm.com>
Reviewed-by: NCornelia Huck <cohuck@redhat.com>
Message-Id: <62e87bf67b38dc8d5760586e7c96d400db854ebe.1562854091.git.alifm@linux.ibm.com>
Reviewed-by: NEric Farman <farman@linux.ibm.com>
Signed-off-by: NCornelia Huck <cohuck@redhat.com>