ACPI / processor_thermal: avoid null pointer deference error

Fix a null pointer deference by acpi_driver_data() if device is
null.  We should only set pr and check this is OK after we are
sure device is not null.

Smatch analysis:

drivers/acpi/processor_thermal.c:223 processor_get_max_state() warn:
  variable dereferenced before check 'device' (see line 221)
drivers/acpi/processor_thermal.c:237 processor_get_cur_state() warn:
  variable dereferenced before check 'device' (see line 235)
drivers/acpi/processor_thermal.c:255 processor_set_cur_state() warn:
  variable dereferenced before check 'device' (see line 251)

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/processor_thermal.c

@@ -218,9 +218,13 @@ processor_get_max_state(struct thermal_cooling_device *cdev,
 			unsigned long *state)
 {
 	struct acpi_device *device = cdev->devdata;
-	struct acpi_processor *pr = acpi_driver_data(device);
+	struct acpi_processor *pr;
 
-	if (!device || !pr)
+	if (!device)
+		return -EINVAL;
+
+	pr = acpi_driver_data(device);
+	if (!pr)
 		return -EINVAL;
 
 	*state = acpi_processor_max_state(pr);
@@ -232,9 +236,13 @@ processor_get_cur_state(struct thermal_cooling_device *cdev,
 			unsigned long *cur_state)
 {
 	struct acpi_device *device = cdev->devdata;
-	struct acpi_processor *pr = acpi_driver_data(device);
+	struct acpi_processor *pr;
 
-	if (!device || !pr)
+	if (!device)
+		return -EINVAL;
+
+	pr = acpi_driver_data(device);
+	if (!pr)
 		return -EINVAL;
 
 	*cur_state = cpufreq_get_cur_state(pr->id);
@@ -248,11 +256,15 @@ processor_set_cur_state(struct thermal_cooling_device *cdev,
 			unsigned long state)
 {
 	struct acpi_device *device = cdev->devdata;
-	struct acpi_processor *pr = acpi_driver_data(device);
+	struct acpi_processor *pr;
 	int result = 0;
 	int max_pstate;
 
-	if (!device || !pr)
+	if (!device)
+		return -EINVAL;
+
+	pr = acpi_driver_data(device);
+	if (!pr)
 		return -EINVAL;
 
 	max_pstate = cpufreq_get_max_state(pr->id);