linux-kernel - [PATCH] USB: core: Fix a NULL pointer dereference

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Message-ID: <AS8P192MB12697886EC8DF1650AD56A57E8EDA@AS8P192MB1269.EURP192.PROD.OUTLOOK.COM>
Date:   Fri,  8 Sep 2023 21:09:37 +0530
From:   Yuran Pereira <yuran.pereira@...mail.com>
To:     gregkh@...uxfoundation.org
Cc:     Yuran Pereira <yuran.pereira@...mail.com>,
        stern@...land.harvard.edu, royluo@...gle.com,
        christophe.jaillet@...adoo.fr, raychi@...gle.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot+c063a4e176681d2e0380@...kaller.appspotmail.com
Subject: [PATCH] USB: core: Fix a NULL pointer dereference


When the call to dev_set_name() in the usb_hub_create_port_device 
function fails to set the device's kobject's name field, 
the subsequent call to device_register() is bound to fail and cause
a NULL pointer derefference, because kobject_add(), which is in the 
call sequence, expects the name field to be set before it is called


This patch adds code to perform error checking for dev_set_name()'s
return value. If the call to dev_set_name() was unsuccessful, 
usb_hub_create_port_device() returns with an error.


PS: The patch also frees port_dev->req and port_dev before returning.
However, I am not sure if that is necessary, because port_dev->req
and port_dev are not freed when device_register() fails. Would be
happy if someone could help me understand why that is, and whether I
should keep those kfree calls in my patch.

dashboard link: https://syzkaller.appspot.com/bug?extid=c063a4e176681d2e0380

Reported-by: syzbot+c063a4e176681d2e0380@...kaller.appspotmail.com

Signed-off-by: Yuran Pereira <yuran.pereira@...mail.com>
---
 drivers/usb/core/port.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index 77be0dc28da9..e546e92e31a7 100644
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -707,8 +707,14 @@ int usb_hub_create_port_device(struct usb_hub *hub, int port1)
 	port_dev->dev.driver = &usb_port_driver;
 	if (hub_is_superspeed(hub->hdev))
 		port_dev->is_superspeed = 1;
-	dev_set_name(&port_dev->dev, "%s-port%d", dev_name(&hub->hdev->dev),
-			port1);
+
+	retval = dev_set_name(&port_dev->dev, "%s-port%d", 
+			dev_name(&hub->hdev->dev), port1);
+	if (retval < 0) {
+		kfree(port_dev->req);
+		kfree(port_dev);
+		return retval;
+	}
 	mutex_init(&port_dev->status_lock);
 	retval = device_register(&port_dev->dev);
 	if (retval) {
-- 
2.25.1