add_partition() does not initialize a partition's read-only policy field, so it
defaults to 0, or read-write, even if the disk itself is flagged read-only.  If
a partition is detected after the call to set_disk_ro() (which sets each
partition's policy field), the partition can be writable, even though the disk
itself is not.

This is known to happen with s390 DASD disks, but could potentially impact other
disk drivers as well.

A simple patch to make the partition inherit the disk's policy field was
accepted upstream and is in the 2.6.18 kernel:

http://marc.theaimsgroup.com/?l=linux-kernel&m=115192926219558&w=2

committed in stream U5 build 42.18. A test kernel with this patch is available
from http://people.redhat.com/~jbaron/rhel4/

This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux maintenance release.  Product Management has requested
further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed
products.  This request is not yet committed for inclusion in an Update
release.

QE ack for RHEL4.5.

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHBA-2007-0304.html