CVE-2026-89442

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

platform/x86: ISST: Validate socket ID in clos_assoc ioctl

isst_if_clos_assoc() validates the user-supplied socket_id with
'socket_id > topology_max_packages()', but isst_common.sst_inst[] is
allocated with topology_max_packages() entries, so the valid index range
is [0, topology_max_packages()).  The '>' comparison lets
socket_id == topology_max_packages() pass and index one entry past the
array.

In addition, isst_common.sst_inst[socket_id] is NULL for an in-range
package that has no bound TPMI SST instance, and the pointer is used
without a NULL check.  Both the out-of-bounds entry and the NULL pointer
are then dereferenced by map_partition_power_domain_id() and the
following power_domain_info access.

Reject socket_id >= topology_max_packages() and a NULL sst_inst, matching
the checks already performed by get_instance().