Re: [PATCH 2.6.10-rc1 3/5] driver-model: sysfs_release() dangling pointer reference fix

[Tejun Heo <tj@home-tj.org>]

 df_03_sysfs_release_fix.patch

 Some attributes are allocated dynamically (e.g. module and device
parameters) and are usually deallocated when the assoicated kobject is
released.  So, it's not safe to access attr after putting the kobject.


Signed-off-by: Tejun Heo <tj@home-tj.org>


Index: linux-export/fs/sysfs/file.c
===================================================================
--- linux-export.orig/fs/sysfs/file.c	2004-11-04 10:25:58.000000000 +0900
+++ linux-export/fs/sysfs/file.c	2004-11-04 11:04:14.000000000 +0900
@@ -330,11 +330,13 @@ static int sysfs_release(struct inode * 
 {
 	struct kobject * kobj = to_kobj(filp->f_dentry->d_parent);
 	struct attribute * attr = to_attr(filp->f_dentry);
+	struct module * owner = attr->owner;
 	struct sysfs_buffer * buffer = filp->private_data;
 
 	if (kobj) 
 		kobject_put(kobj);
-	module_put(attr->owner);
+	/* After this point, attr should not be accessed. */
+	module_put(owner);
 
 	if (buffer) {
 		if (buffer->page)