UPSTREAM: binder: fix incorrect calculation for num_valid

commit 16981742717b04644a41052570fb502682a315d2 upstream.

For BINDER_TYPE_PTR and BINDER_TYPE_FDA transactions, the
num_valid local was calculated incorrectly causing the
range check in binder_validate_ptr() to miss out-of-bounds
offsets.

Fixes: bde4a19fc04f ("binder: use userspace pointer as base of buffer space")
Change-Id: Ida77db13d8e5b726f0b14513f55c2b30277338cd
Signed-off-by: Todd Kjos <tkjos@google.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20191213202531.55010-1-tkjos@google.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Bug: 145988638
Signed-off-by: Todd Kjos <tkjos@google.com>