Re: [PATCH 03/13] power: supply: bq25890: Fix race causing oops at boot

[Sebastian Reichel]

Hi,

On Sat, Oct 30, 2021 at 08:28:03PM +0200, Hans de Goede wrote:
> Before this commit the driver was registering its interrupt handler before
> it registered the power_supply, causing bq->charger to potentially be NULL
> when the interrupt handler runs, triggering a NULL pointer exception in
> the interrupt handler:
> 
> [   21.213531] BUG: kernel NULL pointer dereference, address: 0000000000000680
> ...
> [   21.213573] Hardware name: Xiaomi Inc Mipad2/Mipad, BIOS MIPad-P4.X64.0043.R03.1603071414 03/07/2016
> [   21.213576] RIP: 0010:__lock_acquire+0x5c5/0x1de0
> ...
> [   21.213629] Call Trace:
> [   21.213636]  ? disable_irq_nosync+0x10/0x10
> [   21.213644]  ? __mutex_unlock_slowpath+0x35/0x260
> [   21.213655]  lock_acquire+0xb5/0x2b0
> [   21.213661]  ? power_supply_changed+0x23/0x90
> [   21.213670]  ? disable_irq_nosync+0x10/0x10
> [   21.213676]  _raw_spin_lock_irqsave+0x48/0x60
> [   21.213682]  ? power_supply_changed+0x23/0x90
> [   21.213687]  power_supply_changed+0x23/0x90
> [   21.213697]  __bq25890_handle_irq+0x5e/0xe0 [bq25890_charger]
> [   21.213709]  bq25890_irq_handler_thread+0x26/0x40 [bq25890_charger]
> [   21.213718]  irq_thread_fn+0x20/0x60
> ...
> 
> Fix this by moving the power_supply_register() call to above the
> request_threaded_irq() call.
> 
> Note this fix includes making the following 2 (necessary) changes:
> 
> 1. Switch to the devm version of power_supply_register() to avoid the
> need to make the error-handling in probe() more complicated.
> 
> 2. Rename the "irq_fail" label to "err_unregister_usb_notifier" since
> the old name no longer makes sense after this fix.
> 
> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> ---

Thanks, queued.

-- Sebastian

>  drivers/power/supply/bq25890_charger.c | 23 +++++++++++------------
>  1 file changed, 11 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/power/supply/bq25890_charger.c b/drivers/power/supply/bq25890_charger.c
> index 945c3257ca93..491d36a3811a 100644
> --- a/drivers/power/supply/bq25890_charger.c
> +++ b/drivers/power/supply/bq25890_charger.c
> @@ -734,8 +734,9 @@ static int bq25890_power_supply_init(struct bq25890_device *bq)
>  	psy_cfg.supplied_to = bq25890_charger_supplied_to;
>  	psy_cfg.num_supplicants = ARRAY_SIZE(bq25890_charger_supplied_to);
>  
> -	bq->charger = power_supply_register(bq->dev, &bq25890_power_supply_desc,
> -					    &psy_cfg);
> +	bq->charger = devm_power_supply_register(bq->dev,
> +						 &bq25890_power_supply_desc,
> +						 &psy_cfg);
>  
>  	return PTR_ERR_OR_ZERO(bq->charger);
>  }
> @@ -985,22 +986,22 @@ static int bq25890_probe(struct i2c_client *client,
>  		usb_register_notifier(bq->usb_phy, &bq->usb_nb);
>  	}
>  
> +	ret = bq25890_power_supply_init(bq);
> +	if (ret < 0) {
> +		dev_err(dev, "Failed to register power supply\n");
> +		goto err_unregister_usb_notifier;
> +	}
> +
>  	ret = devm_request_threaded_irq(dev, client->irq, NULL,
>  					bq25890_irq_handler_thread,
>  					IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
>  					BQ25890_IRQ_PIN, bq);
>  	if (ret)
> -		goto irq_fail;
> -
> -	ret = bq25890_power_supply_init(bq);
> -	if (ret < 0) {
> -		dev_err(dev, "Failed to register power supply\n");
> -		goto irq_fail;
> -	}
> +		goto err_unregister_usb_notifier;
>  
>  	return 0;
>  
> -irq_fail:
> +err_unregister_usb_notifier:
>  	if (!IS_ERR_OR_NULL(bq->usb_phy))
>  		usb_unregister_notifier(bq->usb_phy, &bq->usb_nb);
>  
> @@ -1011,8 +1012,6 @@ static int bq25890_remove(struct i2c_client *client)
>  {
>  	struct bq25890_device *bq = i2c_get_clientdata(client);
>  
> -	power_supply_unregister(bq->charger);
> -
>  	if (!IS_ERR_OR_NULL(bq->usb_phy))
>  		usb_unregister_notifier(bq->usb_phy, &bq->usb_nb);
>  
> -- 
> 2.31.1
>

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