From: Uwe Kleine-König u.kleine-koenig@pengutronix.de
[ Upstream commit 7d4edccc9bbfe1dcdff641343f7b0c6763fbe774 ]
Taking a lock at the beginning of .remove() doesn't prevent new readers. With the existing approach it can happen, that a read occurs just when the lock was taken blocking the reader until the lock is released at the end of the remove callback which then accessed *data that is already freed then.
To actually fix this problem the hwmon core needs some adaption. Until this is implemented take the optimistic approach of assuming that all readers are gone after hwmon_device_unregister() and sysfs_remove_group() as most other drivers do. (And once the core implements that, taking the lock would deadlock.)
So drop the lock, move the reset to after device unregistration to keep the device in a workable state until it's deregistered. Also add a error message in case the reset fails and return 0 anyhow. (Returning an error code, doesn't stop the platform device unregistration and only results in a little helpful error message before the devm cleanup handlers are called.)
Signed-off-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de Link: https://lore.kernel.org/r/20220725194344.150098-1-u.kleine-koenig@pengutroni... Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/hwmon/sht15.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-)
diff --git a/drivers/hwmon/sht15.c b/drivers/hwmon/sht15.c index a2fdbb7d20ed..3bff2dce3123 100644 --- a/drivers/hwmon/sht15.c +++ b/drivers/hwmon/sht15.c @@ -1040,25 +1040,20 @@ static int sht15_probe(struct platform_device *pdev) static int sht15_remove(struct platform_device *pdev) { struct sht15_data *data = platform_get_drvdata(pdev); + int ret;
- /* - * Make sure any reads from the device are done and - * prevent new ones beginning - */ - mutex_lock(&data->read_lock); - if (sht15_soft_reset(data)) { - mutex_unlock(&data->read_lock); - return -EFAULT; - } hwmon_device_unregister(data->hwmon_dev); sysfs_remove_group(&pdev->dev.kobj, &sht15_attr_group); + + ret = sht15_soft_reset(data); + if (ret) + dev_err(&pdev->dev, "Failed to reset device (%pe)\n", ERR_PTR(ret)); + if (!IS_ERR(data->reg)) { regulator_unregister_notifier(data->reg, &data->nb); regulator_disable(data->reg); }
- mutex_unlock(&data->read_lock); - return 0; }