linux-kernel - [RFC PATCH 11/11] driver/int3400_thermal: Fix prototype matching

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Date:   Tue, 19 Apr 2022 17:42:41 -0700
From:   joao@...rdrivepizza.com
To:     linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Cc:     joao@...rdrivepizza.com, peterz@...radead.org, jpoimboe@...hat.com,
        andrew.cooper3@...rix.com, keescook@...omium.org,
        samitolvanen@...gle.com, mark.rutland@....com, hjl.tools@...il.com,
        alyssa.milburn@...ux.intel.com, ndesaulniers@...gle.com,
        gabriel.gomes@...ux.intel.com, rick.p.edgecombe@...el.com
Subject: [RFC PATCH 11/11] driver/int3400_thermal: Fix prototype matching

From: Joao Moreira <joao@...rdrivepizza.com>

The function attr_dev_show directly invokes functions from drivers
expecting an specific prototype. The driver for int3400_thermal
implements the given show function using a different prototype than what
is expected. This violates the prototype-based fine-grained CFI policy.

Make the function prototype compliant and cast the respective assignement
so it can be properly user together with fine-grained CFI.

(FWIIW, there should be a less ugly patch for this, but I don't know
enough about the touched source code).

Signed-off-by: Joao Moreira <joao@...rdrivepizza.com>
---
 .../thermal/intel/int340x_thermal/int3400_thermal.c    | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/thermal/intel/int340x_thermal/int3400_thermal.c b/drivers/thermal/intel/int340x_thermal/int3400_thermal.c
index 4954800b9850..4bd95a2016b7 100644
--- a/drivers/thermal/intel/int340x_thermal/int3400_thermal.c
+++ b/drivers/thermal/intel/int340x_thermal/int3400_thermal.c
@@ -311,12 +311,13 @@ static int int3400_thermal_get_uuids(struct int3400_thermal_priv *priv)
 	return result;
 }
 
-static ssize_t odvp_show(struct kobject *kobj, struct kobj_attribute *attr,
+static ssize_t odvp_show(struct device *kobj, struct device_attribute *attr,
 			 char *buf)
 {
+	struct kobj_attribute *kattr = (struct kobj_attribute *) attr;
 	struct odvp_attr *odvp_attr;
 
-	odvp_attr = container_of(attr, struct odvp_attr, attr);
+	odvp_attr = container_of(kattr, struct odvp_attr, attr);
 
 	return sprintf(buf, "%d\n", odvp_attr->priv->odvp[odvp_attr->odvp]);
 }
@@ -388,7 +389,10 @@ static int evaluate_odvp(struct int3400_thermal_priv *priv)
 				goto out_err;
 			}
 			odvp->attr.attr.mode = 0444;
-			odvp->attr.show = odvp_show;
+			odvp->attr.show = (ssize_t (*)
+					(struct kobject *,
+					 struct kobj_attribute *,
+					 char *)) odvp_show;
 			odvp->attr.store = NULL;
 			ret = sysfs_create_file(&priv->pdev->dev.kobj,
 						&odvp->attr.attr);
-- 
2.35.1