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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Amitoj Kaur Chawla <amitoj1606@gmail.com>,
        Johan Hovold <johan@kernel.org>, Pavel Machek <pavel@ucw.cz>
Subject: [PATCH 4.19 15/48] leds: wm831x-status: fix use-after-free on unbind
Date:   Mon, 10 Aug 2020 17:21:37 +0200
Message-Id: <20200810151804.963646027@linuxfoundation.org>
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From: Johan Hovold <johan@kernel.org>

commit 47a459ecc800a17109d0c496a4e21e478806ee40 upstream.

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@vger.kernel.org>     # 4.6
Cc: Amitoj Kaur Chawla <amitoj1606@gmail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/leds/leds-wm831x-status.c |   14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

--- a/drivers/leds/leds-wm831x-status.c
+++ b/drivers/leds/leds-wm831x-status.c
@@ -273,12 +273,23 @@ static int wm831x_status_probe(struct pl
 	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;
 }
 
@@ -287,6 +298,7 @@ static struct platform_driver wm831x_sta
 		   .name = "wm831x-status",
 		   },
 	.probe = wm831x_status_probe,
+	.remove = wm831x_status_remove,
 };
 
 module_platform_driver(wm831x_status_driver);