ACPI: processor: Avoid NULL pointer dereferences at init time

If there are neither processor objects nor processor device objects
in the ACPI tables, the per-CPU processors table will not be
initialized and attempting to dereference pointers from there will
cause the kernel to crash.  This happens in acpi_processor_ppc_init()
and acpi_thermal_cpufreq_init() after commit d15ce412737a ("ACPI:
cpufreq: Switch to QoS requests instead of cpufreq notifier")
which didn't add the requisite NULL pointer checks in there.

Add the NULL pointer checks to acpi_processor_ppc_init() and
acpi_thermal_cpufreq_init(), and to the corresponding "exit"
routines.

While at it, drop redundant return instructions from
acpi_processor_ppc_init() and acpi_thermal_cpufreq_init().

Fixes: d15ce412737a ("ACPI: cpufreq: Switch to QoS requests instead of cpufreq notifier")
Reported-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
index 2261713d1aec..930a49fa4dfc 100644
--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -162,21 +162,23 @@ void acpi_processor_ppc_init(int cpu)
 	struct acpi_processor *pr = per_cpu(processors, cpu);
 	int ret;
 
+	if (!pr)
+		return;
+
 	ret = dev_pm_qos_add_request(get_cpu_device(cpu),
 				     &pr->perflib_req, DEV_PM_QOS_MAX_FREQUENCY,
 				     INT_MAX);
-	if (ret < 0) {
+	if (ret < 0)
 		pr_err("Failed to add freq constraint for CPU%d (%d)\n", cpu,
 		       ret);
-		return;
-	}
 }
 
 void acpi_processor_ppc_exit(int cpu)
 {
 	struct acpi_processor *pr = per_cpu(processors, cpu);
 
-	dev_pm_qos_remove_request(&pr->perflib_req);
+	if (pr)
+		dev_pm_qos_remove_request(&pr->perflib_req);
 }
 
 static int acpi_processor_get_performance_control(struct acpi_processor *pr)