In the Linux kernel, the following vulnerability has been resolved:
iommu/s390: Fix NULL dereference in iova_to_phys() with ZPCI_TABLE_TYPE_RFX
When using a 5-level translation table via ZPCI_TABLE_TYPE_RFX
get_rso_from_iova() returns NULL when the region-first entry is invalid.
Yet in get_rto_from_iova() the region-second origin rso is not checked
to be non-NULL before accessing rso[rsx] leading to a NULL pointer
dereference instead of a NULL return when iova_to_phys() is called on
a unmapped IOVA. Fix this by adding the missing NULL check.
