Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230329133600.908723-1-yajun.deng@linux.dev>
In-Reply-To: <20230329133600.908723-1-yajun.deng@linux.dev>
From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Wed, 29 Mar 2023 16:21:38 +0200
Message-ID: <CAJZ5v0iWkJw3KP7sfyDOyYsEkdOxxPhkYiYZMvd78geofGEECQ@mail.gmail.com>
Subject: Re: [PATCH] cpufreq: Fix policy->freq_table is NULL in __cpufreq_driver_target()
To:     Yajun Deng <yajun.deng@linux.dev>
Cc:     rafael@kernel.org, viresh.kumar@linaro.org,
        linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8BIT
Precedence: bulk

On Wed, Mar 29, 2023 at 3:36 PM Yajun Deng <yajun.deng@linux.dev> wrote:
>
> __resolve_freq() may be return target_freq if policy->freq_table is
> NULL. In this case, it should return -EINVAL before __target_index().

Even so, __target_index() itself doesn't dereference freq_table
AFAICS, so arguably the driver should be prepared to deal with a NULL
freq_table which comes from it after all.

Or, if you want to argue that drivers providing ->target_index() must
also provide freq_table that is not NULL, a check to that effect needs
to be done at the driver registration time IMO.

> Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
> ---
>  drivers/cpufreq/cpufreq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index c0e5be0fe2d6..308a3df1a940 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2299,7 +2299,7 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
>                 return cpufreq_driver->target(policy, target_freq, relation);
>         }
>
> -       if (!cpufreq_driver->target_index)
> +       if (!cpufreq_driver->target_index || !policy->freq_table)
>                 return -EINVAL;
>
>         return __target_index(policy, policy->cached_resolved_idx);
> --