ACPI: CPPC: Avoid out of bounds access when parsing _CPC data

stable inclusion
from stable-4.19.238
commit 28d5387c1994f5e1e0d41b30a1f3dd6e1f609252
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5A6BA
CVE: NA

--------------------------------

commit 40d8abf3 upstream.

If the NumEntries field in the _CPC return package is less than 2, do
not attempt to access the "Revision" element of that package, because
it may not be present then.

Fixes: 337aadff ("ACPI: Introduce CPU performance controls using CPPC")
BugLink: https://lore.kernel.org/lkml/20220322143534.GC32582@xsang-OptiPlex-9020/Reported-by: Nkernel test robot <oliver.sang@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: NHuang Rui <ray.huang@amd.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

drivers/acpi/cppc_acpi.c

@@ -827,6 +827,11 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
 	cpc_obj = &out_obj->package.elements[0];
 	if (cpc_obj->type == ACPI_TYPE_INTEGER)	{
 		num_ent = cpc_obj->integer.value;
+		if (num_ent <= 1) {
+			pr_debug("Unexpected _CPC NumEntries value (%d) for CPU:%d\n",
+				 num_ent, pr->id);
+			goto out_free;
+		}
 	} else {
 		pr_debug("Unexpected entry type(%d) for NumEntries\n",
 				cpc_obj->type);