CVE-2025-39939

In the Linux kernel, the following vulnerability has been resolved:

iommu/s390: Fix memory corruption when using identity domain

zpci_get_iommu_ctrs() returns counter information to be reported as part

of device statistics; these counters are stored as part of the s390_domain.

The problem, however, is that the identity domain is not backed by an

s390_domain and so the conversion via to_s390_domain() yields a bad address

that is zero'd initially and read on-demand later via a sysfs read.

These counters aren't necessary for the identity domain; just return NULL

in this case.

This issue was discovered via KASAN with reports that look like:

BUG: KASAN: global-out-of-bounds in zpci_fmb_enable_device

when using the identity domain for a device on s390.