linux-kernel - [PATCH v2 3/5] extcon: extcon-max77693.c: Fix potential work-queue cancellation race

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Date:   Tue, 18 May 2021 15:32:41 +0300
From:   Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
To:     Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Matti Vaittinen <mazziesaccount@...il.com>
Cc:     hanwoo Choi <cw00.choi@...sung.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/5] extcon: extcon-max77693.c: Fix potential work-queue
 cancellation race

The extcon IRQ schedules a work item. IRQ is requested using devm while
WQ is cancelld at remove(). This mixing of devm and manual unwinding has
potential case where the WQ has been emptied (.remove() was ran) but
devm unwinding of IRQ was not yet done. It may be possible the IRQ is
triggered at this point scheduling new work item to the already flushed
queue.

According to the input documentation the input device allocated by
devm_input_allocate_device() does not need to be explicitly unregistered.
Use the new devm_work_autocancel() and remove the remove() to simplify the
code.

Signed-off-by: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
---

Please note that the change is compile-tested only. All proper testing is
highly appreciated.
---
 drivers/extcon/extcon-max77693.c | 17 +++++------------
 1 file changed, 5 insertions(+), 12 deletions(-)

diff --git a/drivers/extcon/extcon-max77693.c b/drivers/extcon/extcon-max77693.c
index 92af97e00828..1f1d9ab0c5c7 100644
--- a/drivers/extcon/extcon-max77693.c
+++ b/drivers/extcon/extcon-max77693.c
@@ -5,6 +5,7 @@
 // Copyright (C) 2012 Samsung Electrnoics
 // Chanwoo Choi <cw00.choi@...sung.com>
 
+#include <linux/devm-helpers.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/i2c.h>
@@ -1127,7 +1128,10 @@ static int max77693_muic_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, info);
 	mutex_init(&info->mutex);
 
-	INIT_WORK(&info->irq_work, max77693_muic_irq_work);
+	ret = devm_work_autocancel(&pdev->dev, &info->irq_work,
+				   max77693_muic_irq_work);
+	if (ret)
+		return ret;
 
 	/* Support irq domain for MAX77693 MUIC device */
 	for (i = 0; i < ARRAY_SIZE(muic_irqs); i++) {
@@ -1254,22 +1258,11 @@ static int max77693_muic_probe(struct platform_device *pdev)
 	return ret;
 }
 
-static int max77693_muic_remove(struct platform_device *pdev)
-{
-	struct max77693_muic_info *info = platform_get_drvdata(pdev);
-
-	cancel_work_sync(&info->irq_work);
-	input_unregister_device(info->dock);
-
-	return 0;
-}
-
 static struct platform_driver max77693_muic_driver = {
 	.driver		= {
 		.name	= DEV_NAME,
 	},
 	.probe		= max77693_muic_probe,
-	.remove		= max77693_muic_remove,
 };
 
 module_platform_driver(max77693_muic_driver);
-- 
2.25.4


-- 
Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland SWDC
Kiviharjunlenkki 1E
90220 OULU
FINLAND

~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~
Simon says - in Latin please.
~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
Thanks to Simon Glass for the translation =] 

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