From 7f1a57fdd6cb6e7be2ed31878a34655df38e1861 Mon Sep 17 00:00:00 2001 From: Krzysztof Kozlowski Date: Tue, 19 May 2015 16:13:02 +0900 Subject: [PATCH] power_supply: Fix possible NULL pointer dereference on early uevent 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 Signed-off-by: Krzysztof Kozlowski Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core") Tested-By: Dr. H. Nikolaus Schaller Signed-off-by: Sebastian Reichel --- drivers/power/power_supply_core.c | 50 +++++++++++++++++++++++++++---- include/linux/power_supply.h | 1 + 2 files changed, 46 insertions(+), 5 deletions(-) diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c index 15da277e0e8d..4bc0c7f459a5 100644 --- 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_supply *psy) } 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 @@ -645,6 +671,10 @@ __power_supply_register(struct device *parent, 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 *parent, 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 *parent, * 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(struct device *dev, void *res) /** * 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_register); /** * 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 power_supply *psy) { 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); diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h index 75a1dd8dc56e..a80f1fd01ddb 100644 --- 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;