commit 8160c4e4 upstream.

Calling return copy_to_user(...) in an ioctl will not
do the right thing if there's a pagefault:
copy_to_user returns the number of bytes not copied
in this case.

Fix up vfio to do
	return copy_to_user(...)) ?
		-EFAULT : 0;

everywhere.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
[ luis: backported to 3.16:
  - dropped changes to vfio_platform_common.c ]
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>