CVE-2026-64070

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

powerpc/hv-gpci: fix preempt count leak in sysfs show paths

Four sysfs show() callbacks in hv-gpci take get_cpu_var(hv_gpci_reqb)
(which calls preempt_disable()) but only call the matching put_cpu_var()
on the error path under the 'out:' label. Every successful read leaks
one preempt_disable():

  processor_bus_topology_show()
  processor_config_show()
  affinity_domain_via_virtual_processor_show()
  affinity_domain_via_domain_show()

(affinity_domain_via_partition_show() was already correct.)

On a CONFIG_PREEMPT=y kernel, repeated reads raise preempt_count and
eventually return to userspace with preemption still disabled. The
next user-mode page fault then hits faulthandler_disabled() == 1,
gets forced to SIGSEGV, and the resulting coredump trips
'BUG: scheduling while atomic' in call_usermodehelper_exec ->
wait_for_completion_state -> schedule:

  BUG: scheduling while atomic: <task>/<pid>/0x00000004
  ...
  __schedule_bug+0x6c/0x90
  __schedule+0x58c/0x13a0
  schedule+0x48/0x1a0
  schedule_timeout+0x104/0x170
  wait_for_completion_state+0x16c/0x330
  call_usermodehelper_exec+0x254/0x2d0
  vfs_coredump+0x1050/0x2590
  get_signal+0xb9c/0xc80
  do_notify_resume+0xf8/0x470

Add an out_success label that calls put_cpu_var() before returning
the byte count, mirroring affinity_domain_via_partition_show().