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Date:   Thu, 30 Mar 2023 01:39:18 +0000
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From:   "Yajun Deng" <yajun.deng@linux.dev>
Message-ID: <b0e52380c54775073d44bc97f823ec4f@linux.dev>
Subject: Re: [PATCH] cpufreq: Fix policy->freq_table is NULL in
 __cpufreq_driver_target()
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     viresh.kumar@linaro.org, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org
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 <20230329133600.908723-1-yajun.deng@linux.dev>
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March 29, 2023 10:21 PM, "Rafael J. Wysocki" <rafael@kernel.org> wrote:=
=0A=0A> On Wed, Mar 29, 2023 at 3:36 PM Yajun Deng <yajun.deng@linux.dev>=
 wrote:=0A> =0A>> __resolve_freq() may be return target_freq if policy->f=
req_table is=0A>> NULL. In this case, it should return -EINVAL before __t=
arget_index().=0A> =0A> Even so, __target_index() itself doesn't derefere=
nce freq_table=0A> AFAICS, so arguably the driver should be prepared to d=
eal with a NULL=0A> freq_table which comes from it after all.=0A> =0A=0AB=
ut there is a statement 'unsigned int newfreq =3D policy->freq_table[inde=
x].frequency;'=0Ain __target_index(), if driver doesn't provide freq_tabl=
e, __target_index()=0Awill fault before the driver itself.=0A=0A> Or, if =
you want to argue that drivers providing ->target_index() must=0A> also p=
rovide freq_table that is not NULL, a check to that effect needs=0A> to b=
e done at the driver registration time IMO.=0A> =0A>> Signed-off-by: Yaju=
n Deng <yajun.deng@linux.dev>=0A>> ---=0A>> drivers/cpufreq/cpufreq.c | 2=
 +-=0A>> 1 file changed, 1 insertion(+), 1 deletion(-)=0A>> =0A>> diff --=
git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c=0A>> index c0=
e5be0fe2d6..308a3df1a940 100644=0A>> --- a/drivers/cpufreq/cpufreq.c=0A>>=
 +++ b/drivers/cpufreq/cpufreq.c=0A>> @@ -2299,7 +2299,7 @@ int __cpufreq=
_driver_target(struct cpufreq_policy *policy,=0A>> return cpufreq_driver-=
>target(policy, target_freq, relation);=0A>> }=0A>> =0A>> - if (!cpufreq_=
driver->target_index)=0A>> + if (!cpufreq_driver->target_index || !policy=
->freq_table)=0A>> return -EINVAL;=0A>> =0A>> return __target_index(polic=
y, policy->cached_resolved_idx);=0A>> --