patch "USB: adutux: fix use-after-free on disconnect" added to usb-linus

This is a note to let you know that I've just added the patch titled

USB: adutux: fix use-after-free on disconnect

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 44efc269db7929f6275a1fa927ef082e533ecde0 Mon Sep 17 00:00:00 2001
From: Johan Hovold <[email protected]>
Date: Wed, 25 Sep 2019 11:29:12 +0200
Subject: USB: adutux: fix use-after-free on disconnect

The driver was clearing its struct usb_device pointer, which it used as an inverted disconnected flag, before deregistering the character device and without serialising against racing release().

This could lead to a use-after-free if a racing release() callback observes the cleared pointer and frees the driver data before disconnect() is finished with it.

This could also lead to NULL-pointer dereferences in a racing open().

---
 drivers/usb/misc/adutux.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

index 344d523b0502..bcc138990e2f 100644
@@ -762,14 +762,15 @@ static void adu_disconnect(struct usb_interface *interface)
 
 	dev = usb_get_intfdata(interface);
 
-	mutex_lock(&dev->mtx);	/* not interruptible */
-	dev->udev = NULL;	/* poison */
 	usb_deregister_dev(interface, &adu_class);
-	mutex_unlock(&dev->mtx);
 
 	mutex_lock(&adutux_mutex);
 	usb_set_intfdata(interface, NULL);
 
+	mutex_lock(&dev->mtx);	/* not interruptible */
+	dev->udev = NULL;	/* poison */
+	mutex_unlock(&dev->mtx);
+
 	/* if the device is not opened, then we clean up right now */
 	if (!dev->open_count)
 		adu_delete(dev);

2.23.0