ACPI / CPPC: Fix per-CPU pointer management in acpi_cppc_processor_probe()

Fix a possible use-after-free scenario in acpi_cppc_processor_probe()
that can happen if the function returns without cleaning up the
per-CPU pointer set by it previously.

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/cppc_acpi.c

@@ -776,9 +776,6 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 		init_waitqueue_head(&pcc_data.pcc_write_wait_q);
 	}
 
-	/* Plug PSD data into this CPUs CPC descriptor. */
-	per_cpu(cpc_desc_ptr, pr->id) = cpc_ptr;
-
 	/* Everything looks okay */
 	pr_debug("Parsed CPC struct for CPU: %d\n", pr->id);
 
@@ -789,10 +786,15 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 		goto out_free;
 	}
 
+	/* Plug PSD data into this CPUs CPC descriptor. */
+	per_cpu(cpc_desc_ptr, pr->id) = cpc_ptr;
+
 	ret = kobject_init_and_add(&cpc_ptr->kobj, &cppc_ktype, &cpu_dev->kobj,
 			"acpi_cppc");
-	if (ret)
+	if (ret) {
+		per_cpu(cpc_desc_ptr, pr->id) = NULL;
 		goto out_free;
+	}
 
 	kfree(output.pointer);
 	return 0;