linux-kernel - [PATCH] device-core: Ensure drvdata = NULL when no driver is bound

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Date:	Wed, 23 May 2012 00:09:34 +0200
From:	Hans de Goede <hdegoede@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Jiri Slaby <jslaby@...e.cz>, Jiri Kosina <jkosina@...e.cz>,
	USB list <linux-usb@...r.kernel.org>,
	Hans de Goede <hdegoede@...hat.com>
Subject: [PATCH] device-core: Ensure drvdata = NULL when no driver is bound

1) drvdata is for a driver to store a pointer to driver specific data
2) If no driver is bound, there is no driver specific data associated with
   the device
3) Thus logically drvdata should be NULL if no driver is bound.

But many drivers don't clear drvdata on device_release, or set drvdata
early on in probe and leave it set on probe error. Both of which results
in a dangling pointer in drvdata.

This patch enforce for drvdata to be NULL after device_release or on probe
failure.

Signed-off-by: Hans de Goede <hdegoede@...hat.com>
---
 drivers/base/dd.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 1b1cbb5..9a1e970 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -283,6 +283,7 @@ probe_failed:
 	devres_release_all(dev);
 	driver_sysfs_remove(dev);
 	dev->driver = NULL;
+	dev_set_drvdata(dev, NULL);
 
 	if (ret == -EPROBE_DEFER) {
 		/* Driver requested deferred probing */
@@ -487,6 +488,7 @@ static void __device_release_driver(struct device *dev)
 			drv->remove(dev);
 		devres_release_all(dev);
 		dev->driver = NULL;
+		dev_set_drvdata(dev, NULL);
 		klist_remove(&dev->p->knode_driver);
 		if (dev->bus)
 			blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
-- 
1.7.10

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