cpufreq: scmi: Fix null-ptr-deref in scmi_cpufreq_get_rate()

cpufreq_cpu_get_raw() can return NULL when the target CPU is not present
in the policy->cpus mask. scmi_cpufreq_get_rate() does not check for
this case, which results in a NULL pointer dereference.

Add NULL check after cpufreq_cpu_get_raw() to prevent this issue.

Fixes: 99d6bdf ("cpufreq: add support for CPU DVFS based on SCMI message protocol")
Signed-off-by: Henry Martin <bsdhenrymartin@gmail.com>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

Author: Henry Martin

drivers/cpufreq/scmi-cpufreq.c

@@ -37,11 +37,17 @@ static struct cpufreq_driver scmi_cpufreq_driver;
 
 static unsigned int scmi_cpufreq_get_rate(unsigned int cpu)
 {
-	struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
-	struct scmi_data *priv = policy->driver_data;
+	struct cpufreq_policy *policy;
+	struct scmi_data *priv;
 	unsigned long rate;
 	int ret;
 
+	policy = cpufreq_cpu_get_raw(cpu);
+	if (unlikely(!policy))
+		return 0;
+
+	priv = policy->driver_data;
+
 	ret = perf_ops->freq_get(ph, priv->domain_id, &rate, false);
 	if (ret)
 		return 0;