USB: legousbtower: fix use-after-free on release

BugLink: https://bugs.launchpad.net/bugs/1850541
commit 726b55d0e22ca72c69c947af87785c830289ddbc upstream.

The driver was accessing its struct usb_device in its release()
callback without holding a reference. This would lead to a
use-after-free whenever the device was disconnected while the character
device was still open.

Fixes: fef526cae700 ("USB: legousbtower: remove custom debug macro")
Cc: stable <stable@vger.kernel.org>     # 3.12
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191009153848.8664-5-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/usb/misc/legousbtower.c b/drivers/usb/misc/legousbtower.c
index 4214d336f778813bc85f100a415e5720c7c669fd..5418f3a8c50ab5f9ec1aeec118d95dcfd939b3ac 100644 (file)
--- a/drivers/usb/misc/legousbtower.c
+++ b/drivers/usb/misc/legousbtower.c
@@ -296,6 +296,7 @@ static inline void tower_delete (struct lego_usb_tower *dev)
        kfree (dev->read_buffer);
        kfree (dev->interrupt_in_buffer);
        kfree (dev->interrupt_out_buffer);
+       usb_put_dev(dev->udev);
        kfree (dev);
 }
 
@@ -809,7 +810,7 @@ static int tower_probe (struct usb_interface *interface, const struct usb_device
 
        mutex_init(&dev->lock);
 
-       dev->udev = udev;
+       dev->udev = usb_get_dev(udev);
        dev->open_count = 0;
        dev->disconnected = 0;