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

[Mario Limonciello]

On 8/8/2024 08:07, Anastasia Belova wrote:
> 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?

FWIW, I don't really like it either.  As it's amd-pstate code I'd say 
Gautham and I should make the call.

Can you please change it to avoid mixing code and declarations?

> > 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