[4/6] power: supply: sc27xx: Fix external_power_changed race

sc27xx_fgu_external_power_changed() dereferences data->battery,
which gets sets in ab8500_btemp_probe() like this:

	data->battery = devm_power_supply_register(dev, &sc27xx_fgu_desc,
                                                   &fgu_cfg);

As soon as devm_power_supply_register() has called device_add()
the external_power_changed callback can get called. So there is a window
where sc27xx_fgu_external_power_changed() may get called while
data->battery has not been set yet leading to a NULL pointer dereference.

Fixing this is easy. The external_power_changed callback gets passed
the power_supply which will eventually get stored in data->battery,
so sc27xx_fgu_external_power_changed() can simply directly use
the passed in psy argument which is always valid.

After this change sc27xx_fgu_external_power_changed() is reduced to just
"power_supply_changed(psy);" and it has the same prototype. While at it
simply replace it with making the external_power_changed callback
directly point to power_supply_changed.

Cc: Orson Zhai <orsonzhai@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Note this has been compile tested only
---
 drivers/power/supply/sc27xx_fuel_gauge.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

On 4/16/2023 12:07 AM, Hans de Goede wrote:
> sc27xx_fgu_external_power_changed() dereferences data->battery,
> which gets sets in ab8500_btemp_probe() like this:
> 
> 	data->battery = devm_power_supply_register(dev, &sc27xx_fgu_desc,
>                                                     &fgu_cfg);
> 
> As soon as devm_power_supply_register() has called device_add()
> the external_power_changed callback can get called. So there is a window
> where sc27xx_fgu_external_power_changed() may get called while
> data->battery has not been set yet leading to a NULL pointer dereference.
> 
> Fixing this is easy. The external_power_changed callback gets passed
> the power_supply which will eventually get stored in data->battery,
> so sc27xx_fgu_external_power_changed() can simply directly use
> the passed in psy argument which is always valid.
> 
> After this change sc27xx_fgu_external_power_changed() is reduced to just
> "power_supply_changed(psy);" and it has the same prototype. While at it
> simply replace it with making the external_power_changed callback
> directly point to power_supply_changed.
> 
> Cc: Orson Zhai <orsonzhai@gmail.com>
> Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
> Cc: Chunyan Zhang <zhang.lyra@gmail.com>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Looks good to me. Thanks.
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>

> ---
> Note this has been compile tested only
> ---
>   drivers/power/supply/sc27xx_fuel_gauge.c | 9 +--------
>   1 file changed, 1 insertion(+), 8 deletions(-)
> 
> diff --git a/drivers/power/supply/sc27xx_fuel_gauge.c b/drivers/power/supply/sc27xx_fuel_gauge.c
> index 632977f84b95..bd23c4d9fed4 100644
> --- a/drivers/power/supply/sc27xx_fuel_gauge.c
> +++ b/drivers/power/supply/sc27xx_fuel_gauge.c
> @@ -733,13 +733,6 @@ static int sc27xx_fgu_set_property(struct power_supply *psy,
>   	return ret;
>   }
>   
> -static void sc27xx_fgu_external_power_changed(struct power_supply *psy)
> -{
> -	struct sc27xx_fgu_data *data = power_supply_get_drvdata(psy);
> -
> -	power_supply_changed(data->battery);
> -}
> -
>   static int sc27xx_fgu_property_is_writeable(struct power_supply *psy,
>   					    enum power_supply_property psp)
>   {
> @@ -774,7 +767,7 @@ static const struct power_supply_desc sc27xx_fgu_desc = {
>   	.num_properties		= ARRAY_SIZE(sc27xx_fgu_props),
>   	.get_property		= sc27xx_fgu_get_property,
>   	.set_property		= sc27xx_fgu_set_property,
> -	.external_power_changed	= sc27xx_fgu_external_power_changed,
> +	.external_power_changed	= power_supply_changed,
>   	.property_is_writeable	= sc27xx_fgu_property_is_writeable,
>   	.no_thermal		= true,
>   };