power: supply: cros_charge-control: add mutex for driver data

Concurrent accesses through sysfs may lead to inconsistent state in the
priv data. Introduce a mutex to avoid this.

Fixes: c6ed48e ("power: supply: add ChromeOS EC based charge control driver")
Cc: [email protected]
Signed-off-by: Thomas Weißschuh <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sebastian Reichel <[email protected]>

Author: t-8ch

drivers/power/supply/cros_charge-control.c

@@ -7,8 +7,10 @@
 #include <acpi/battery.h>
 #include <linux/container_of.h>
 #include <linux/dmi.h>
+#include <linux/lockdep.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/platform_data/cros_ec_commands.h>
 #include <linux/platform_data/cros_ec_proto.h>
 #include <linux/platform_device.h>
@@ -49,6 +51,7 @@ struct cros_chctl_priv {
 	struct attribute *attributes[_CROS_CHCTL_ATTR_COUNT];
 	struct attribute_group group;
 
+	struct mutex lock; /* protects fields below and cros_ec */
 	enum power_supply_charge_behaviour current_behaviour;
 	u8 current_start_threshold, current_end_threshold;
 };
@@ -85,6 +88,8 @@ static int cros_chctl_configure_ec(struct cros_chctl_priv *priv)
 {
 	struct ec_params_charge_control req = {};
 
+	lockdep_assert_held(&priv->lock);
+
 	req.cmd = EC_CHARGE_CONTROL_CMD_SET;
 
 	switch (priv->current_behaviour) {
@@ -159,6 +164,7 @@ static ssize_t charge_control_start_threshold_show(struct device *dev,
 	struct cros_chctl_priv *priv = cros_chctl_attr_to_priv(&attr->attr,
 							       CROS_CHCTL_ATTR_START_THRESHOLD);
 
+	guard(mutex)(&priv->lock);
 	return sysfs_emit(buf, "%u\n", (unsigned int)priv->current_start_threshold);
 }
 
@@ -169,6 +175,7 @@ static ssize_t charge_control_start_threshold_store(struct device *dev,
 	struct cros_chctl_priv *priv = cros_chctl_attr_to_priv(&attr->attr,
 							       CROS_CHCTL_ATTR_START_THRESHOLD);
 
+	guard(mutex)(&priv->lock);
 	return cros_chctl_store_threshold(dev, priv, 0, buf, count);
 }
 
@@ -178,6 +185,7 @@ static ssize_t charge_control_end_threshold_show(struct device *dev, struct devi
 	struct cros_chctl_priv *priv = cros_chctl_attr_to_priv(&attr->attr,
 							       CROS_CHCTL_ATTR_END_THRESHOLD);
 
+	guard(mutex)(&priv->lock);
 	return sysfs_emit(buf, "%u\n", (unsigned int)priv->current_end_threshold);
 }
 
@@ -187,6 +195,7 @@ static ssize_t charge_control_end_threshold_store(struct device *dev, struct dev
 	struct cros_chctl_priv *priv = cros_chctl_attr_to_priv(&attr->attr,
 							       CROS_CHCTL_ATTR_END_THRESHOLD);
 
+	guard(mutex)(&priv->lock);
 	return cros_chctl_store_threshold(dev, priv, 1, buf, count);
 }
 
@@ -195,6 +204,7 @@ static ssize_t charge_behaviour_show(struct device *dev, struct device_attribute
 	struct cros_chctl_priv *priv = cros_chctl_attr_to_priv(&attr->attr,
 							       CROS_CHCTL_ATTR_CHARGE_BEHAVIOUR);
 
+	guard(mutex)(&priv->lock);
 	return power_supply_charge_behaviour_show(dev, EC_CHARGE_CONTROL_BEHAVIOURS,
 						  priv->current_behaviour, buf);
 }
@@ -210,6 +220,7 @@ static ssize_t charge_behaviour_store(struct device *dev, struct device_attribut
 	if (ret < 0)
 		return ret;
 
+	guard(mutex)(&priv->lock);
 	priv->current_behaviour = ret;
 
 	ret = cros_chctl_configure_ec(priv);
@@ -290,6 +301,10 @@ static int cros_chctl_probe(struct platform_device *pdev)
 	if (!priv)
 		return -ENOMEM;
 
+	ret = devm_mutex_init(dev, &priv->lock);
+	if (ret)
+		return ret;
+
 	ret = cros_ec_get_cmd_versions(cros_ec, EC_CMD_CHARGE_CONTROL);
 	if (ret < 0)
 		return ret;
@@ -327,7 +342,8 @@ static int cros_chctl_probe(struct platform_device *pdev)
 	priv->current_end_threshold = 100;
 
 	/* Bring EC into well-known state */
-	ret = cros_chctl_configure_ec(priv);
+	scoped_guard(mutex, &priv->lock)
+		ret = cros_chctl_configure_ec(priv);
 	if (ret < 0)
 		return ret;