linux-kernel - [PATCH 2/4] extcon: extcon-max14577: Fix potential work-queue cancellation race

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Message-ID: <70dfbe28725bac3383f77d02037f4f7f37839989.1620633360.git.matti.vaittinen@fi.rohmeurope.com>
Date:   Mon, 10 May 2021 11:11:42 +0300
From:   Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
To:     Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Matti Vaittinen <mazziesaccount@...il.com>
Cc:     Chanwoo 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 2/4] extcon: extcon-max14577: 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 is possible the IRQ is triggered
at this point scheduling new work item to the already flushed queue.

Use new devm_work_autocancel() to remove the remove() and to kill the bug.

Signed-off-by: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
---

Please note that the change is compile-tested only. All proper testing is
highly appreciated.
---
 drivers/extcon/extcon-max14577.c | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/drivers/extcon/extcon-max14577.c b/drivers/extcon/extcon-max14577.c
index ace523924e58..5476f48ed74b 100644
--- a/drivers/extcon/extcon-max14577.c
+++ b/drivers/extcon/extcon-max14577.c
@@ -6,6 +6,7 @@
 // Chanwoo Choi <cw00.choi@...sung.com>
 // Krzysztof Kozlowski <krzk@...nel.org>
 
+#include <linux/devm-helpers.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/i2c.h>
@@ -673,7 +674,10 @@ static int max14577_muic_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, info);
 	mutex_init(&info->mutex);
 
-	INIT_WORK(&info->irq_work, max14577_muic_irq_work);
+	ret = devm_work_autocancel(&pdev->dev, &info->irq_work,
+				   max14577_muic_irq_work);
+	if (ret)
+		return ret;
 
 	switch (max14577->dev_type) {
 	case MAXIM_DEVICE_TYPE_MAX77836:
@@ -766,15 +770,6 @@ static int max14577_muic_probe(struct platform_device *pdev)
 	return ret;
 }
 
-static int max14577_muic_remove(struct platform_device *pdev)
-{
-	struct max14577_muic_info *info = platform_get_drvdata(pdev);
-
-	cancel_work_sync(&info->irq_work);
-
-	return 0;
-}
-
 static const struct platform_device_id max14577_muic_id[] = {
 	{ "max14577-muic", MAXIM_DEVICE_TYPE_MAX14577, },
 	{ "max77836-muic", MAXIM_DEVICE_TYPE_MAX77836, },
@@ -797,7 +792,6 @@ static struct platform_driver max14577_muic_driver = {
 		.of_match_table = of_max14577_muic_dt_match,
 	},
 	.probe		= max14577_muic_probe,
-	.remove		= max14577_muic_remove,
 	.id_table	= max14577_muic_id,
 };
 
-- 
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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