From 40d8abf364bcab23bc715a9221a3c8623956257b Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Date: Tue, 22 Mar 2022 17:02:05 +0100
Subject: [PATCH] ACPI: CPPC: Avoid out of bounds access when parsing _CPC data
Git-commit: 40d8abf364bcab23bc715a9221a3c8623956257b
Patch-mainline: v5.18-rc1
References: git-fixes

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: 337aadff8e45 ("ACPI: Introduce CPU performance controls using CPPC")
Buglink: https://lore.kernel.org/lkml/20220322143534.GC32582@xsang-OptiPlex-9020/
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Huang Rui <ray.huang@amd.com>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/acpi/cppc_acpi.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index d418449194ee..b97af8a722e7 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -679,6 +679,11 @@ 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);
-- 
2.31.1