linux-kernel - [PATCH] driver core: class: properly reference count class_dev

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Date:   Tue, 16 May 2023 21:20:14 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-usb@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        syzbot+e7afd76ad060fa0d2605@...kaller.appspotmail.com,
        Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Alan Stern <stern@...land.harvard.edu>
Subject: [PATCH] driver core: class: properly reference count class_dev_iter()

When class_dev_iter is initialized, the reference count for the subsys
private structure is incremented, but never decremented, causing a
memory leak over time.  To resolve this, save off a pointer to the
internal structure into the class_dev_iter structure and then when the
iterator is finished, drop the reference count.

Reported-and-tested-by: syzbot+e7afd76ad060fa0d2605@...kaller.appspotmail.com
Reported-by: Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Alan Stern <stern@...land.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/base/class.c         | 2 ++
 include/linux/device/class.h | 1 +
 2 files changed, 3 insertions(+)

diff --git a/drivers/base/class.c b/drivers/base/class.c
index ac1808d1a2e8..05d9df90f621 100644
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -320,6 +320,7 @@ void class_dev_iter_init(struct class_dev_iter *iter, const struct class *class,
 		start_knode = &start->p->knode_class;
 	klist_iter_init_node(&sp->klist_devices, &iter->ki, start_knode);
 	iter->type = type;
+	iter->sp = sp;
 }
 EXPORT_SYMBOL_GPL(class_dev_iter_init);
 
@@ -361,6 +362,7 @@ EXPORT_SYMBOL_GPL(class_dev_iter_next);
 void class_dev_iter_exit(struct class_dev_iter *iter)
 {
 	klist_iter_exit(&iter->ki);
+	subsys_put(iter->sp);
 }
 EXPORT_SYMBOL_GPL(class_dev_iter_exit);
 
diff --git a/include/linux/device/class.h b/include/linux/device/class.h
index 9deeaeb457bb..abf3d3bfb6fe 100644
--- a/include/linux/device/class.h
+++ b/include/linux/device/class.h
@@ -74,6 +74,7 @@ struct class {
 struct class_dev_iter {
 	struct klist_iter		ki;
 	const struct device_type	*type;
+	struct subsys_private		*sp;
 };
 
 int __must_check class_register(const struct class *class);
-- 
2.40.1