block: RCU protect disk->conv_zones_bitmap

In the Linux kernel, the following vulnerability has been resolved: block: RCU protect disk->conv_zones_bitmap Ensure that a disk revalidation changing the conventional zones bitmap of a disk does not cause invalid memory references when using the disk_zone_is_conv() helper by RCU protecting the disk->conv_zones_bitmap pointer. disk_zone_is_conv() is modified to operate under the RCU read lock and the function disk_set_conv_zones_bitmap() is added to update a disk conv_zones_bitmap pointer using rcu_replace_pointer() with the disk zone_wplugs_lock spinlock held. disk_free_zone_resources() is modified to call disk_update_zone_resources() with a NULL bitmap pointer to free the disk conv_zones_bitmap. disk_set_conv_zones_bitmap() is also used in disk_update_zone_resources() to set the new (revalidated) bitmap and free the old one.