Patch "hwmon: (sht15) Fix wrong assumptions in device remove callback" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    hwmon: (sht15) Fix wrong assumptions in device remove callback

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     hwmon-sht15-fix-wrong-assumptions-in-device-remove-c.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit eeb2c8e54dd37082a17c4486e5e54c4de8e3040f
Author: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Date:   Mon Jul 25 21:43:44 2022 +0200

    hwmon: (sht15) Fix wrong assumptions in device remove callback
    
    [ 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@xxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20220725194344.150098-1-u.kleine-koenig@xxxxxxxxxxxxxx
    Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/hwmon/sht15.c b/drivers/hwmon/sht15.c
index 7f4a63959730..ae4d14257a11 100644
--- a/drivers/hwmon/sht15.c
+++ b/drivers/hwmon/sht15.c
@@ -1020,25 +1020,20 @@ 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;
 }