cppc_cpufreq: Fix possible null pointer dereference

jira LE-1907
cve CVE-2024-38573
Rebuild_History Non-Buildable kernel-5.14.0-427.37.1.el9_4
commit-author Aleksandr Mishin <amishin@t-argos.ru>
commit cf7de25

cppc_cpufreq_get_rate() and hisi_cppc_cpufreq_get_rate() can be called from
different places with various parameters. So cpufreq_cpu_get() can return
null as 'policy' in some circumstances.
Fix this bug by adding null return check.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: a28b2bf ("cppc_cpufreq: replace per-cpu data array with a list")
	Signed-off-by: Aleksandr Mishin <amishin@t-argos.ru>
	Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
(cherry picked from commit cf7de25)
	Signed-off-by: Jonathan Maple <jmaple@ciq.com>

Author: PlaidCat

drivers/cpufreq/cppc_cpufreq.c

@@ -841,10 +841,15 @@ static unsigned int cppc_cpufreq_get_rate(unsigned int cpu)
 {
 	struct cppc_perf_fb_ctrs fb_ctrs_t0 = {0}, fb_ctrs_t1 = {0};
 	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
-	struct cppc_cpudata *cpu_data = policy->driver_data;
+	struct cppc_cpudata *cpu_data;
 	u64 delivered_perf;
 	int ret;
 
+	if (!policy)
+		return -ENODEV;
+
+	cpu_data = policy->driver_data;
+
 	cpufreq_cpu_put(policy);
 
 	ret = cppc_get_perf_ctrs(cpu, &fb_ctrs_t0);
@@ -924,10 +929,15 @@ static struct cpufreq_driver cppc_cpufreq_driver = {
 static unsigned int hisi_cppc_cpufreq_get_rate(unsigned int cpu)
 {
 	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
-	struct cppc_cpudata *cpu_data = policy->driver_data;
+	struct cppc_cpudata *cpu_data;
 	u64 desired_perf;
 	int ret;
 
+	if (!policy)
+		return -ENODEV;
+
+	cpu_data = policy->driver_data;
+
 	cpufreq_cpu_put(policy);
 
 	ret = cppc_get_desired_perf(cpu, &desired_perf);