linux-kernel - [PATCH 2/6] leds: da903x: fix use-after-free on unbind

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Date:   Mon,  1 Jun 2020 15:39:46 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Pavel Machek <pavel@....cz>
Cc:     Dan Murphy <dmurphy@...com>,
        Amitoj Kaur Chawla <amitoj1606@...il.com>,
        linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
        Johan Hovold <johan@...nel.org>,
        stable <stable@...r.kernel.org>
Subject: [PATCH 2/6] leds: da903x: fix use-after-free on unbind

Several MFD child drivers register their class devices directly under
the parent device. This means you cannot blindly do devres conversions
so that deregistration ends up being tied to the parent device,
something which leads to use-after-free on driver unbind when the class
device is released while still being registered.

Fixes: eed16255d66b ("leds: da903x: Use devm_led_classdev_register")
Cc: stable <stable@...r.kernel.org>     # 4.6
Cc: Amitoj Kaur Chawla <amitoj1606@...il.com>
Signed-off-by: Johan Hovold <johan@...nel.org>
---
 drivers/leds/leds-da903x.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/leds/leds-da903x.c b/drivers/leds/leds-da903x.c
index ed1b303f699f..2b5fb00438a2 100644
--- a/drivers/leds/leds-da903x.c
+++ b/drivers/leds/leds-da903x.c
@@ -110,12 +110,23 @@ static int da903x_led_probe(struct platform_device *pdev)
 	led->flags = pdata->flags;
 	led->master = pdev->dev.parent;
 
-	ret = devm_led_classdev_register(led->master, &led->cdev);
+	ret = led_classdev_register(led->master, &led->cdev);
 	if (ret) {
 		dev_err(&pdev->dev, "failed to register LED %d\n", id);
 		return ret;
 	}
 
+	platform_set_drvdata(pdev, led);
+
+	return 0;
+}
+
+static int da903x_led_remove(struct platform_device *pdev)
+{
+	struct da903x_led *led = platform_get_drvdata(pdev);
+
+	led_classdev_unregister(&led->cdev);
+
 	return 0;
 }
 
@@ -124,6 +135,7 @@ static struct platform_driver da903x_led_driver = {
 		.name	= "da903x-led",
 	},
 	.probe		= da903x_led_probe,
+	.remove		= da903x_led_remove,
 };
 
 module_platform_driver(da903x_led_driver);
-- 
2.26.2