device_schedule_callback() needs a module reference

This patch (as896b) fixes an oversight in the design of
device_schedule_callback().  It is necessary to acquire a reference to the
module owning the callback routine, to prevent the module from being
unloaded before the callback can run.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Satyam Sharma <satyam.sharma@gmail.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 11 insertions, 3 deletions

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index fc4633378dc..db0413a411d 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -633,6 +633,7 @@ struct sysfs_schedule_callback_struct {
 	struct kobject 		*kobj;
 	void			(*func)(void *);
 	void			*data;
+	struct module		*owner;
 	struct work_struct	work;
 };
 
@@ -643,6 +644,7 @@ static void sysfs_schedule_callback_work(struct work_struct *work)
 
 	(ss->func)(ss->data);
 	kobject_put(ss->kobj);
+	module_put(ss->owner);
 	kfree(ss);
 }
 
@@ -651,6 +653,7 @@ static void sysfs_schedule_callback_work(struct work_struct *work)
  * @kobj: object we're acting for.
  * @func: callback function to invoke later.
  * @data: argument to pass to @func.
+ * @owner: module owning the callback code
  *
  * sysfs attribute methods must not unregister themselves or their parent
  * kobject (which would amount to the same thing).  Attempts to do so will
@@ -663,20 +666,25 @@ static void sysfs_schedule_callback_work(struct work_struct *work)
  * until @func returns.
  *
  * Returns 0 if the request was submitted, -ENOMEM if storage could not
- * be allocated.
+ * be allocated, -ENODEV if a reference to @owner isn't available.
  */
 int sysfs_schedule_callback(struct kobject *kobj, void (*func)(void *),
-		void *data)
+		void *data, struct module *owner)
 {
 	struct sysfs_schedule_callback_struct *ss;
 
+	if (!try_module_get(owner))
+		return -ENODEV;
 	ss = kmalloc(sizeof(*ss), GFP_KERNEL);
-	if (!ss)
+	if (!ss) {
+		module_put(owner);
 		return -ENOMEM;
+	}
 	kobject_get(kobj);
 	ss->kobj = kobj;
 	ss->func = func;
 	ss->data = data;
+	ss->owner = owner;
 	INIT_WORK(&ss->work, sysfs_schedule_callback_work);
 	schedule_work(&ss->work);
 	return 0;