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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 <hns@goldelico.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Fixes: 297d716f62 ("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>
This commit is contained in:
Krzysztof Kozlowski 2015-05-19 16:13:02 +09:00 committed by Sebastian Reichel
parent 8e59c7f234
commit 7f1a57fdd6
2 changed files with 46 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
drivers/power/power_supply_core.c
View File

@ -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 <linux/of.h>
@ -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);

1
include/linux/power_supply.h
View File

@ -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;