Re: [PATCH] cpufreq: acpi-cpufreq: add NULL check for acpi_perf_data before freeing

On 8/10/2026 2:10 PM, lirongqing wrote:
> From: Li RongQing <[email protected]>
> 
> If alloc_percpu() fails in acpi_cpufreq_early_init(), acpi_perf_data is
> NULL.  Calling free_acpi_perf_data() will execute per_cpu_ptr(NULL, i),
> which does not return NULL but an offset pointer.

Hi RongQing,

Could you please confirm if acpi_perf_data() can ever be executed when 
alloc_percpu() fails?


> Dereferencing ->shared_cpu_map on this invalid pointer leads to a kernel
> crash.
> 
> Fix these issues by adding a NULL check at the start of
> free_acpi_perf_data() and setting acpi_perf_data to NULL after freeing.
> 
> Signed-off-by: Li RongQing <[email protected]>
> ---
>   drivers/cpufreq/acpi-cpufreq.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> index 87e4923..cd2ca87 100644
> --- a/drivers/cpufreq/acpi-cpufreq.c
> +++ b/drivers/cpufreq/acpi-cpufreq.c
> @@ -517,11 +517,14 @@ static void free_acpi_perf_data(void)
>   {
>   	unsigned int i;
>   
> -	/* Freeing a NULL pointer is OK, and alloc_percpu zeroes. */
> +	if (!acpi_perf_data)
> +		return;
> +
>   	for_each_possible_cpu(i)
>   		free_cpumask_var(per_cpu_ptr(acpi_perf_data, i)
>   				 ->shared_cpu_map);
>   	free_percpu(acpi_perf_data);
> +	acpi_perf_data = NULL;
>   }
>   
>   static int cpufreq_boost_down_prep(unsigned int cpu)


-- 
Thx and BRs,
Zhongqiu Han