commit c877cdce upstream.

copy_to_user() returns the number of bytes remaining to be copied and
I'm pretty sure we want to return a negative error code here.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>