It is possible for user space to attempt to attach a valid fd that does not correspond to a genlock file. This change adds a magic to the kernel private data that is used for validation. CRs-fixed: 359649 Change-Id: Idb16056ba0f89b7d519d501f5b1ce6d5d930ed70 Signed-off-by: Jeff Boody <jboody@codeaurora.org>