linux-kernel - [PATCH 5/6] leds: wm831x-status: fix use-after-free on unbind

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Message-Id: <20200601133950.12420-6-johan@kernel.org>
Date:   Mon,  1 Jun 2020 15:39:49 +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 5/6] leds: wm831x-status: 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: 8d3b6a4001ce ("leds: wm831x-status: 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-wm831x-status.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/leds/leds-wm831x-status.c b/drivers/leds/leds-wm831x-status.c
index 082df7f1dd90..67f4235cb28a 100644
--- a/drivers/leds/leds-wm831x-status.c
+++ b/drivers/leds/leds-wm831x-status.c
@@ -269,12 +269,23 @@ static int wm831x_status_probe(struct platform_device *pdev)
 	drvdata->cdev.blink_set = wm831x_status_blink_set;
 	drvdata->cdev.groups = wm831x_status_groups;
 
-	ret = devm_led_classdev_register(wm831x->dev, &drvdata->cdev);
+	ret = led_classdev_register(wm831x->dev, &drvdata->cdev);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "Failed to register LED: %d\n", ret);
 		return ret;
 	}
 
+	platform_set_drvdata(pdev, drvdata);
+
+	return 0;
+}
+
+static int wm831x_status_remove(struct platform_device *pdev)
+{
+	struct wm831x_status *drvdata = platform_get_drvdata(pdev);
+
+	led_classdev_unregister(&drvdata->cdev);
+
 	return 0;
 }
 
@@ -283,6 +294,7 @@ static struct platform_driver wm831x_status_driver = {
 		   .name = "wm831x-status",
 		   },
 	.probe = wm831x_status_probe,
+	.remove = wm831x_status_remove,
 };
 
 module_platform_driver(wm831x_status_driver);
-- 
2.26.2