linux-kernel - Re: [PATCH] cpufreq: amd-pstate: add check for cpufreq_cpu

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Message-ID: <69c57210-8a48-4ae2-b529-a4cd6dbd0121@astralinux.ru>
Date: Thu, 8 Aug 2024 16:07:19 +0300
From: Anastasia Belova <abelova@...ralinux.ru>
To: "Gautham R. Shenoy" <gautham.shenoy@....com>
Cc: Huang Rui <ray.huang@....com>,
 Mario Limonciello <mario.limonciello@....com>,
 Perry Yuan <perry.yuan@....com>, "Rafael J. Wysocki" <rafael@...nel.org>,
 Viresh Kumar <viresh.kumar@...aro.org>, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH] cpufreq: amd-pstate: add check for cpufreq_cpu_get's
 return value

Hello,

06/06/24 12:55, Gautham R. Shenoy пишет:
> Hello,
>
> On Mon, Jun 03, 2024 at 02:07:41PM +0300, Anastasia Belova wrote:
>> cpufreq_cpu_get may return NULL. To avoid NULL-dereference check it
>> and return in case of error.
>>
>> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>>
>> Signed-off-by: Anastasia Belova <abelova@...ralinux.ru>
> Thank you for the patch. Indeed we should be checking if the policy is
> valid before dereferencing it.
>
>> ---
>>   drivers/cpufreq/amd-pstate.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
>> index 1b7e82a0ad2e..672cb6c280a4 100644
>> --- a/drivers/cpufreq/amd-pstate.c
>> +++ b/drivers/cpufreq/amd-pstate.c
>> @@ -621,6 +621,8 @@ static void amd_pstate_adjust_perf(unsigned int cpu,
>>   	unsigned long max_perf, min_perf, des_perf,
>>   		      cap_perf, lowest_nonlinear_perf, max_freq;
>>   	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
>> +	if (!policy)
>> +		return;
> This patch mixes code and declarations. While I personally don't
> prefer that, since we have moved to using C99, the compiler does
> not complain, nor does checkpatch complain.
>
> So is this ok for cpufreq, Rafael?

Should I form the second version without mixing code and declarations?
Or it is better to wait for Rafael's answer?

>
> Or would you prefer something like:
>
> 	unsigned long cap_perf, lowest_nonlinear_perf;
> 	unsigned long max_perf, min_perf, des_perf;
> 	struct cpufreq_policy *policy;
> 	struct amd_cpudata *cpudata;
> 	unsigned int target_freq;
> 	unsigned long max_freq;
>
> 	policy = cpufreq_cpu_get(cpu);
> 	if (!policy)
> 		return;
>
> 	cpudata = policy->driver_data;
>
>
>
>>   	struct amd_cpudata *cpudata = policy->driver_data;
>>   	unsigned int target_freq;
>>   
>> @@ -777,6 +779,8 @@ static void amd_pstate_init_prefcore(struct amd_cpudata *cpudata)
>>   static void amd_pstate_update_limits(unsigned int cpu)
>>   {
>>   	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
>> +	if (!policy)
>> +		return;
> Ditto.
>
>>   	struct amd_cpudata *cpudata = policy->driver_data;
>>   	u32 prev_high = 0, cur_high = 0;
>>   	int ret;
>> -- 
>> 2.30.2
>>
> --
> Thanks and Regards
> gautham.

Thanks,
Anastasia Belova