Re: [PATCH] ACPI: processor: idle: Fix NULL pointer dereference in hotplug path

[Rafael J. Wysocki]

On Fri, Apr 3, 2026 at 11:03 AM Huisong Li <lihuisong@xxxxxxxxxx> wrote:
>
> A cpuidle_device might fail to register during boot, but the system can
> continue to run. In such cases, acpi_processor_hotplug() can trigger
> a NULL pointer dereference when accessing the per-cpu acpi_cpuidle_device.
>
> So add NULL pointer check for the per-cpu acpi_cpuidle_device in
> acpi_processor_hotplug.
>
> Signed-off-by: Huisong Li <lihuisong@xxxxxxxxxx>
> ---
>  drivers/acpi/processor_idle.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index 479995a4c48a..2adaee0f32ed 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -1267,16 +1267,15 @@ static int acpi_processor_get_power_info(struct acpi_processor *pr)
>
>  int acpi_processor_hotplug(struct acpi_processor *pr)
>  {
> +       struct cpuidle_device *dev = per_cpu(acpi_cpuidle_device, pr->id);
>         int ret = 0;
> -       struct cpuidle_device *dev;
>
>         if (disabled_by_idle_boot_param())
>                 return 0;
>
> -       if (!pr->flags.power_setup_done)
> +       if (!pr->flags.power_setup_done || !dev)
>                 return -ENODEV;
>
> -       dev = per_cpu(acpi_cpuidle_device, pr->id);
>         cpuidle_pause_and_lock();
>         cpuidle_disable_device(dev);
>         ret = acpi_processor_get_power_info(pr);
> --

Applied as 7.1 material, thanks!