linux-kernel - [PATCH v3] usb: stkwebcam: Update the reference count of the usb device structure

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Date:   Wed, 1 Sep 2021 20:46:49 +0800
From:   Cai Huoqing <caihuoqing@...du.com>
To:     <caihuoqing@...du.com>
CC:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        <linux-media@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v3] usb: stkwebcam: Update the reference count of the usb device structure

Use usb_get_dev() to increment the reference count of the usb device
structure in order to avoid releasing the structure while it is still in
use. And use usb_put_dev() to decrement the reference count and thus,
when it will be equal to 0 the structure will be released.

Signed-off-by: Cai Huoqing <caihuoqing@...du.com>
---
v2->v3:
*call usb_put_dev() in the error path of stk_camera_probe
*move v4l2_ctrl_handler_free/v4l2_device_unregister/kfree(dev)
 from stk_camera_disconnect() to stk_v4l_dev_release()
 
drivers/media/usb/stkwebcam/stk-webcam.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/media/usb/stkwebcam/stk-webcam.c b/drivers/media/usb/stkwebcam/stk-webcam.c
index 0e231e576dc3..9f445e6ab5fa 100644
--- a/drivers/media/usb/stkwebcam/stk-webcam.c
+++ b/drivers/media/usb/stkwebcam/stk-webcam.c
@@ -1234,6 +1234,11 @@ static void stk_v4l_dev_release(struct video_device *vd)
 	if (dev->sio_bufs != NULL || dev->isobufs != NULL)
 		pr_err("We are leaking memory\n");
 	usb_put_intf(dev->interface);
+	usb_put_dev(dev->udev);
+
+	v4l2_ctrl_handler_free(&dev->hdl);
+	v4l2_device_unregister(&dev->v4l2_dev);
+	kfree(dev);
 }
 
 static const struct video_device stk_v4l_data = {
@@ -1309,7 +1314,7 @@ static int stk_camera_probe(struct usb_interface *interface,
 	init_waitqueue_head(&dev->wait_frame);
 	dev->first_init = 1; /* webcam LED management */
 
-	dev->udev = udev;
+	dev->udev = usb_get_dev(udev);
 	dev->interface = interface;
 	usb_get_intf(interface);
 
@@ -1365,6 +1370,7 @@ static int stk_camera_probe(struct usb_interface *interface,
 
 error_put:
 	usb_put_intf(interface);
+	usb_put_dev(dev->udev);
 error:
 	v4l2_ctrl_handler_free(hdl);
 	v4l2_device_unregister(&dev->v4l2_dev);
@@ -1385,9 +1391,6 @@ static void stk_camera_disconnect(struct usb_interface *interface)
 		video_device_node_name(&dev->vdev));
 
 	video_unregister_device(&dev->vdev);
-	v4l2_ctrl_handler_free(&dev->hdl);
-	v4l2_device_unregister(&dev->v4l2_dev);
-	kfree(dev);
 }
 
 #ifdef CONFIG_PM
-- 
2.25.1