linux-kernel - [PATCH] driver-core: don't free devt

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Message-ID: <46432FFD.1040304@gmail.com>
Date:	Thu, 10 May 2007 16:45:17 +0200
From:	Tejun Heo <htejun@...il.com>
To:	Greg KH <greg@...ah.com>
CC:	Chris Rankin <rankincj@...oo.com>,
	Alan Stern <stern@...land.harvard.edu>,
	linux-usb-devel@...ts.sourceforge.net,
	linux-kernel <linux-kernel@...r.kernel.org>, stable@...nel.org
Subject: [PATCH] driver-core: don't free devt_attr till the device is released

Currently, devt_attr for the "dev" file is freed immediately on device
removal, but if the "dev" sysfs file is open when a device is removed,
sysfs will access its attribute structure for further access including
close resulting in jumping to garbled address.  Fix it by postponing
freeing devt_attr to device release time.

Note that devt_attr for class_device is already freed on release.

This bug is reported by Chris Rankin as bugzilla bug#8198.

Signed-off-by: Tejun Heo <htejun@...il.com>
Cc: Chris Rankin <rankincj@...oo.com>
---
Applies well to 2.6.20 and 21.  As sysfs-immediate-disconnect doesn't
seem to be included in 2.6.22, this should be included in linus#master
too (applies well there as well).

* This is the second post.  Something went wrong with the recipients
  list on the first posting.  Both are same.

Thanks.

 drivers/base/core.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Index: tree0/drivers/base/core.c
===================================================================
--- tree0.orig/drivers/base/core.c
+++ tree0/drivers/base/core.c
@@ -93,6 +93,9 @@ static void device_release(struct kobjec
 {
 	struct device * dev = to_dev(kobj);
 
+	kfree(dev->devt_attr);
+	dev->devt_attr = NULL;
+
 	if (dev->release)
 		dev->release(dev);
 	else if (dev->class && dev->class->dev_release)
@@ -650,10 +653,8 @@ void device_del(struct device * dev)
 
 	if (parent)
 		klist_del(&dev->knode_parent);
-	if (dev->devt_attr) {
+	if (dev->devt_attr)
 		device_remove_file(dev, dev->devt_attr);
-		kfree(dev->devt_attr);
-	}
 	if (dev->class) {
 		sysfs_remove_link(&dev->kobj, "subsystem");
 		/* If this is not a "fake" compatible device, remove the
-
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