linux-kernel - [PATCH v2] usb: misc: fix improper handling of refcount in uss720

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Date:   Thu,  7 Apr 2022 10:40:01 +0800
From:   Hangyu Hua <hbh25y@...il.com>
To:     gregkh@...uxfoundation.org, mudongliangabcd@...il.com,
        oneukum@...e.com
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hangyu Hua <hbh25y@...il.com>
Subject: [PATCH v2] usb: misc: fix improper handling of refcount in uss720_probe()

usb_put_dev shouldn't be called when uss720_probe succeeds because of
priv->usbdev. At the same time, priv->usbdev shouldn't be set to NULL
before destroy_priv in uss720_disconnect because usb_put_dev is in
destroy_priv.

Fix this by moving priv->usbdev = NULL after usb_put_dev.

Fixes: dcb4b8ad6a44 ("misc/uss720: fix memory leak in uss720_probe")
Signed-off-by: Hangyu Hua <hbh25y@...il.com>
---

v2: fix a stupid UAF in the previous version.

 drivers/usb/misc/uss720.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/misc/uss720.c b/drivers/usb/misc/uss720.c
index 748139d26263..0be8efcda15d 100644
--- a/drivers/usb/misc/uss720.c
+++ b/drivers/usb/misc/uss720.c
@@ -71,6 +71,7 @@ static void destroy_priv(struct kref *kref)
 
 	dev_dbg(&priv->usbdev->dev, "destroying priv datastructure\n");
 	usb_put_dev(priv->usbdev);
+	priv->usbdev = NULL;
 	kfree(priv);
 }
 
@@ -736,7 +737,6 @@ static int uss720_probe(struct usb_interface *intf,
 	parport_announce_port(pp);
 
 	usb_set_intfdata(intf, pp);
-	usb_put_dev(usbdev);
 	return 0;
 
 probe_abort:
@@ -754,7 +754,6 @@ static void uss720_disconnect(struct usb_interface *intf)
 	usb_set_intfdata(intf, NULL);
 	if (pp) {
 		priv = pp->private_data;
-		priv->usbdev = NULL;
 		priv->pp = NULL;
 		dev_dbg(&intf->dev, "parport_remove_port\n");
 		parport_remove_port(pp);
-- 
2.25.1