Re: [PATCH] cpufreq: amd-pstate: add check for cpufreq_cpu_get's return value

[Anastasia Belova]

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@xxxxxxxxxxxxx>
> 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