[PATCH] driver core: class: properly reference count class_dev_iter()

From: Greg Kroah-Hartman
Date: Tue May 16 2023 - 15:20:26 EST


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@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: Mirsad Goran Todorovac <mirsad.todorovac@xxxxxxxxxxxx>
Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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