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Subject[PATCH 4.1 32/65] power_supply: Fix possible NULL pointer dereference on early uevent
Date
4.1-stable review patch.  If anyone has any objections, please let me know.

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

From: Krzysztof Kozlowski <k.kozlowski@samsung.com>

commit 7f1a57fdd6cb6e7be2ed31878a34655df38e1861 upstream.

Don't call the power_supply_changed() from power_supply_register() when
parent is still probing because it may lead to accessing parent too
early.

In bq27x00_battery this caused NULL pointer exception because uevent of
power_supply_changed called back the the get_property() method provided
by the driver. The get_property() method accessed pointer which should
be returned by power_supply_register().

Starting from bq27x00_battery_probe():
di->bat = power_supply_register()
power_supply_changed()
kobject_uevent()
power_supply_uevent()
power_supply_show_property()
power_supply_get_property()
bq27x00_battery_get_property()
dereference of di->bat which is NULL here

The dereference of di->bat (value returned by power_supply_register())
is the currently visible problem. However calling back the methods
provided by driver before ending the probe may lead to accessing other
driver-related data which is not yet initialized.

The call to power_supply_changed() is postponed till probing ends -
mutex of parent device is released.

Reported-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
Tested-By: Dr. H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/power/power_supply_core.c | 50 ++++++++++++++++++++++++++++++++++----
include/linux/power_supply.h | 1
2 files changed, 46 insertions(+), 5 deletions(-)

--- a/drivers/power/power_supply_core.c
+++ b/drivers/power/power_supply_core.c
@@ -30,6 +30,8 @@ EXPORT_SYMBOL_GPL(power_supply_notifier)

static struct device_type power_supply_dev_type;

+#define POWER_SUPPLY_DEFERRED_REGISTER_TIME msecs_to_jiffies(10)
+
static bool __power_supply_is_supplied_by(struct power_supply *supplier,
struct power_supply *supply)
{
@@ -121,6 +123,30 @@ void power_supply_changed(struct power_s
}
EXPORT_SYMBOL_GPL(power_supply_changed);

+/*
+ * Notify that power supply was registered after parent finished the probing.
+ *
+ * Often power supply is registered from driver's probe function. However
+ * calling power_supply_changed() directly from power_supply_register()
+ * would lead to execution of get_property() function provided by the driver
+ * too early - before the probe ends.
+ *
+ * Avoid that by waiting on parent's mutex.
+ */
+static void power_supply_deferred_register_work(struct work_struct *work)
+{
+ struct power_supply *psy = container_of(work, struct power_supply,
+ deferred_register_work.work);
+
+ if (psy->dev.parent)
+ mutex_lock(&psy->dev.parent->mutex);
+
+ power_supply_changed(psy);
+
+ if (psy->dev.parent)
+ mutex_unlock(&psy->dev.parent->mutex);
+}
+
#ifdef CONFIG_OF
#include <linux/of.h>

@@ -645,6 +671,10 @@ __power_supply_register(struct device *p
struct power_supply *psy;
int rc;

+ if (!parent)
+ pr_warn("%s: Expected proper parent device for '%s'\n",
+ __func__, desc->name);
+
psy = kzalloc(sizeof(*psy), GFP_KERNEL);
if (!psy)
return ERR_PTR(-ENOMEM);
@@ -671,6 +701,8 @@ __power_supply_register(struct device *p
goto dev_set_name_failed;

INIT_WORK(&psy->changed_work, power_supply_changed_work);
+ INIT_DELAYED_WORK(&psy->deferred_register_work,
+ power_supply_deferred_register_work);

rc = power_supply_check_supplies(psy);
if (rc) {
@@ -709,7 +741,10 @@ __power_supply_register(struct device *p
* after calling power_supply_register()).
*/
atomic_inc(&psy->use_cnt);
- power_supply_changed(psy);
+
+ queue_delayed_work(system_power_efficient_wq,
+ &psy->deferred_register_work,
+ POWER_SUPPLY_DEFERRED_REGISTER_TIME);

return psy;

@@ -729,7 +764,8 @@ dev_set_name_failed:

/**
* power_supply_register() - Register new power supply
- * @parent: Device to be a parent of power supply's device
+ * @parent: Device to be a parent of power supply's device, usually
+ * the device which probe function calls this
* @desc: Description of power supply, must be valid through whole
* lifetime of this power supply
* @cfg: Run-time specific configuration accessed during registering,
@@ -750,7 +786,8 @@ EXPORT_SYMBOL_GPL(power_supply_register)

/**
* power_supply_register() - Register new non-waking-source power supply
- * @parent: Device to be a parent of power supply's device
+ * @parent: Device to be a parent of power supply's device, usually
+ * the device which probe function calls this
* @desc: Description of power supply, must be valid through whole
* lifetime of this power supply
* @cfg: Run-time specific configuration accessed during registering,
@@ -779,7 +816,8 @@ static void devm_power_supply_release(st

/**
* power_supply_register() - Register managed power supply
- * @parent: Device to be a parent of power supply's device
+ * @parent: Device to be a parent of power supply's device, usually
+ * the device which probe function calls this
* @desc: Description of power supply, must be valid through whole
* lifetime of this power supply
* @cfg: Run-time specific configuration accessed during registering,
@@ -814,7 +852,8 @@ EXPORT_SYMBOL_GPL(devm_power_supply_regi

/**
* power_supply_register() - Register managed non-waking-source power supply
- * @parent: Device to be a parent of power supply's device
+ * @parent: Device to be a parent of power supply's device, usually
+ * the device which probe function calls this
* @desc: Description of power supply, must be valid through whole
* lifetime of this power supply
* @cfg: Run-time specific configuration accessed during registering,
@@ -858,6 +897,7 @@ void power_supply_unregister(struct powe
{
WARN_ON(atomic_dec_return(&psy->use_cnt));
cancel_work_sync(&psy->changed_work);
+ cancel_delayed_work_sync(&psy->deferred_register_work);
sysfs_remove_link(&psy->dev.kobj, "powers");
power_supply_remove_triggers(psy);
psy_unregister_cooler(psy);
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -237,6 +237,7 @@ struct power_supply {
/* private */
struct device dev;
struct work_struct changed_work;
+ struct delayed_work deferred_register_work;
spinlock_t changed_lock;
bool changed;
atomic_t use_cnt;



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