[PATCH 1/2] power_supply: Use wrappers to avoid races when registering power supply

From: Krzysztof Kozlowski
Date: Tue May 19 2015 - 03:16:55 EST


Use wrappers over get_property() and set_property() internally in power
supply and for sysfs interface. The wrappers provide safe access if
power supply is not yet registered or t is being destroyed.

In case of syfs the theoretical race could happen between ending of
driver's probe and parallel sysfs access:
some_driver_probe() userspace
==================================== ===========================
drv->psy = power_supply_register()
device_add()
sysfs entries are created
atomic_inc(&psy->use_cnt);
store on sysfs attributes
drv->set_property()
dereference of drv->psy
drv->psy = returned psy;

For leds the race could happen between power supply being destroyed and
ongoing power_supply_changed_work().

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
---
drivers/power/power_supply_leds.c | 4 ++--
drivers/power/power_supply_sysfs.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/power/power_supply_leds.c b/drivers/power/power_supply_leds.c
index 2d41a43fc81a..2277ad9c2f68 100644
--- a/drivers/power/power_supply_leds.c
+++ b/drivers/power/power_supply_leds.c
@@ -25,7 +25,7 @@ static void power_supply_update_bat_leds(struct power_supply *psy)
unsigned long delay_on = 0;
unsigned long delay_off = 0;

- if (psy->desc->get_property(psy, POWER_SUPPLY_PROP_STATUS, &status))
+ if (power_supply_get_property(psy, POWER_SUPPLY_PROP_STATUS, &status))
return;

dev_dbg(&psy->dev, "%s %d\n", __func__, status.intval);
@@ -115,7 +115,7 @@ static void power_supply_update_gen_leds(struct power_supply *psy)
{
union power_supply_propval online;

- if (psy->desc->get_property(psy, POWER_SUPPLY_PROP_ONLINE, &online))
+ if (power_supply_get_property(psy, POWER_SUPPLY_PROP_ONLINE, &online))
return;

dev_dbg(&psy->dev, "%s %d\n", __func__, online.intval);
diff --git a/drivers/power/power_supply_sysfs.c b/drivers/power/power_supply_sysfs.c
index 9134e3d2d95e..af026806cba5 100644
--- a/drivers/power/power_supply_sysfs.c
+++ b/drivers/power/power_supply_sysfs.c
@@ -125,7 +125,7 @@ static ssize_t power_supply_store_property(struct device *dev,

value.intval = long_val;

- ret = psy->desc->set_property(psy, off, &value);
+ ret = power_supply_set_property(psy, off, &value);
if (ret < 0)
return ret;

--
1.9.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/