LU-9859 libcfs: double copy bug

LU-9859 libcfs: double copy bug

The problem is that we copy hdr.ioc_len, we verify it, then we copy it
again without checking to see if it has changed in between the two
copies.

This could result in an information leak.

Linux-commit: 76bdaa161cd93d9c033bf6fe2b0a5661c8204441

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Change-Id: Ic9ae8c19d90a5547600f3775ed337394717b94e3
Reviewed-on: https://review.whamcloud.com/35574
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>
Reviewed-by: Oleg Drokin <green@whamcloud.com>