linux-kernel - [PATCH 2/2] thermal: of: fix double-free on unregistration

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Date:   Sat,  8 Jul 2023 13:27:20 +0200
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>
Cc:     kernel@...gutronix.de, Ahmad Fatoum <a.fatoum@...gutronix.de>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] thermal: of: fix double-free on unregistration

Since commit 3d439b1a2ad3 ("thermal/core: Alloc-copy-free the thermal
zone parameters structure"), thermal_zone_device_register() allocates
a copy of the tzp argument and frees it when unregistering, so
thermal_of_zone_register() now ends up leaking its original tzp and
double-freeing the tzp copy. Fix this by locating tzp on stack instead.

Fixes: 3d439b1a2ad3 ("thermal/core: Alloc-copy-free the thermal zone parameters structure")
Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de>
---
 drivers/thermal/thermal_of.c | 27 ++++++---------------------
 1 file changed, 6 insertions(+), 21 deletions(-)

diff --git a/drivers/thermal/thermal_of.c b/drivers/thermal/thermal_of.c
index 6fb14e521197..bc07ae1c284c 100644
--- a/drivers/thermal/thermal_of.c
+++ b/drivers/thermal/thermal_of.c
@@ -238,17 +238,13 @@ static int thermal_of_monitor_init(struct device_node *np, int *delay, int *pdel
 	return 0;
 }
 
-static struct thermal_zone_params *thermal_of_parameters_init(struct device_node *np)
+static void thermal_of_parameters_init(struct device_node *np,
+				       struct thermal_zone_params *tzp)
 {
-	struct thermal_zone_params *tzp;
 	int coef[2];
 	int ncoef = ARRAY_SIZE(coef);
 	int prop, ret;
 
-	tzp = kzalloc(sizeof(*tzp), GFP_KERNEL);
-	if (!tzp)
-		return ERR_PTR(-ENOMEM);
-
 	tzp->no_hwmon = true;
 
 	if (!of_property_read_u32(np, "sustainable-power", &prop))
@@ -267,8 +263,6 @@ static struct thermal_zone_params *thermal_of_parameters_init(struct device_node
 
 	tzp->slope = coef[0];
 	tzp->offset = coef[1];
-
-	return tzp;
 }
 
 static struct device_node *thermal_of_zone_get_by_name(struct thermal_zone_device *tz)
@@ -442,13 +436,11 @@ static int thermal_of_unbind(struct thermal_zone_device *tz,
 static void thermal_of_zone_unregister(struct thermal_zone_device *tz)
 {
 	struct thermal_trip *trips = tz->trips;
-	struct thermal_zone_params *tzp = tz->tzp;
 	struct thermal_zone_device_ops *ops = tz->ops;
 
 	thermal_zone_device_disable(tz);
 	thermal_zone_device_unregister(tz);
 	kfree(trips);
-	kfree(tzp);
 	kfree(ops);
 }
 
@@ -477,7 +469,7 @@ static struct thermal_zone_device *thermal_of_zone_register(struct device_node *
 {
 	struct thermal_zone_device *tz;
 	struct thermal_trip *trips;
-	struct thermal_zone_params *tzp;
+	struct thermal_zone_params tzp = {};
 	struct thermal_zone_device_ops *of_ops;
 	struct device_node *np;
 	int delay, pdelay;
@@ -509,12 +501,7 @@ static struct thermal_zone_device *thermal_of_zone_register(struct device_node *
 		goto out_kfree_trips;
 	}
 
-	tzp = thermal_of_parameters_init(np);
-	if (IS_ERR(tzp)) {
-		ret = PTR_ERR(tzp);
-		pr_err("Failed to initialize parameter from %pOFn: %d\n", np, ret);
-		goto out_kfree_trips;
-	}
+	thermal_of_parameters_init(np, &tzp);
 
 	of_ops->bind = thermal_of_bind;
 	of_ops->unbind = thermal_of_unbind;
@@ -522,12 +509,12 @@ static struct thermal_zone_device *thermal_of_zone_register(struct device_node *
 	mask = GENMASK_ULL((ntrips) - 1, 0);
 
 	tz = thermal_zone_device_register_with_trips(np->name, trips, ntrips,
-						     mask, data, of_ops, tzp,
+						     mask, data, of_ops, &tzp,
 						     pdelay, delay);
 	if (IS_ERR(tz)) {
 		ret = PTR_ERR(tz);
 		pr_err("Failed to register thermal zone %pOFn: %d\n", np, ret);
-		goto out_kfree_tzp;
+		goto out_kfree_trips;
 	}
 
 	ret = thermal_zone_device_enable(tz);
@@ -540,8 +527,6 @@ static struct thermal_zone_device *thermal_of_zone_register(struct device_node *
 
 	return tz;
 
-out_kfree_tzp:
-	kfree(tzp);
 out_kfree_trips:
 	kfree(trips);
 out_kfree_of_ops:
-- 
2.39.2