[PATCH] HID: fix a crash in hid_debug_events_release

[Charles Yi]

hid_debug_events_release() access released memory by
hid_device_release(). This is fixed by the patch.

Signed-off-by: Charles Yi <be286@xxxxxxx>
---
 drivers/hid/hid-core.c  | 12 ++++++++++--
 drivers/hid/hid-debug.c |  3 +++
 include/linux/hid.h     |  3 +++
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 8992e3c1e769..e0181218ad85 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -702,15 +702,22 @@ static void hid_close_report(struct hid_device *device)
  * Free a device structure, all reports, and all fields.
  */
 
-static void hid_device_release(struct device *dev)
+void hiddev_free(struct kref *ref)
 {
-	struct hid_device *hid = to_hid_device(dev);
+	struct hid_device *hid = container_of(ref, struct hid_device, ref);
 
 	hid_close_report(hid);
 	kfree(hid->dev_rdesc);
 	kfree(hid);
 }
 
+static void hid_device_release(struct device *dev)
+{
+	struct hid_device *hid = to_hid_device(dev);
+
+	kref_put(&hid->ref, hiddev_free);
+}
+
 /*
  * Fetch a report description item from the data stream. We support long
  * items, though they are not used yet.
@@ -2846,6 +2853,7 @@ struct hid_device *hid_allocate_device(void)
 	spin_lock_init(&hdev->debug_list_lock);
 	sema_init(&hdev->driver_input_lock, 1);
 	mutex_init(&hdev->ll_open_lock);
+	kref_init(&hdev->ref);
 
 	hid_bpf_device_init(hdev);
 
diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
index e7ef1ea107c9..7dd83ec74f8a 100644
--- a/drivers/hid/hid-debug.c
+++ b/drivers/hid/hid-debug.c
@@ -1135,6 +1135,7 @@ static int hid_debug_events_open(struct inode *inode, struct file *file)
 		goto out;
 	}
 	list->hdev = (struct hid_device *) inode->i_private;
+	kref_get(&list->hdev->ref);
 	file->private_data = list;
 	mutex_init(&list->read_mutex);
 
@@ -1227,6 +1228,8 @@ static int hid_debug_events_release(struct inode *inode, struct file *file)
 	list_del(&list->node);
 	spin_unlock_irqrestore(&list->hdev->debug_list_lock, flags);
 	kfifo_free(&list->hid_debug_fifo);
+
+	kref_put(&list->hdev->ref, hiddev_free);
 	kfree(list);
 
 	return 0;
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 964ca1f15e3f..3b08a2957229 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -679,6 +679,7 @@ struct hid_device {							/* device report descriptor */
 	struct list_head debug_list;
 	spinlock_t  debug_list_lock;
 	wait_queue_head_t debug_wait;
+	struct kref			ref;
 
 	unsigned int id;						/* system unique id */
 
@@ -687,6 +688,8 @@ struct hid_device {							/* device report descriptor */
 #endif /* CONFIG_BPF */
 };
 
+void hiddev_free(struct kref *ref);
+
 #define to_hid_device(pdev) \
 	container_of(pdev, struct hid_device, dev)
 
-- 
2.34.1