In the Linux kernel, the following vulnerability has been resolved: cpufreq: Fix hotplug-suspend race during reboot During system reboot,

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

cpufreq: Fix hotplug-suspend race during reboot

During system reboot, cpufreq_suspend() is called via the
kernel_restart() -> device_shutdown() path. Unlike the normal system
suspend path, the reboot path does not call freeze_processes(), so
userspace processes and kernel threads remain active.

This allows CPU hotplug operations to run concurrently with
cpufreq_suspend(). The original code has no synchronization with CPU
hotplug, leading to a race condition where governor_data can be freed
by the hotplug path while cpufreq_suspend() is still accessing it,
resulting in a null pointer dereference:

Unable to handle kernel NULL pointer dereference
Call Trace:
do_kernel_fault+0x28/0x3c
cpufreq_suspend+0xdc/0x160
device_shutdown+0x18/0x200
kernel_restart+0x40/0x80
arm64_sys_reboot+0x1b0/0x200

Fix this by adding cpus_read_lock()/cpus_read_unlock() to
cpufreq_suspend() to block CPU hotplug operations while suspend is in
progress.

[ rjw: Changelog edits ]