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

Hans de Goede
2021-10-30T18:28:43Z

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@redhat.com>
---
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