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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Johan Hovold <johan@kernel.org>
Subject: [PATCH 4.9 72/92] USB: legousbtower: fix use-after-free on release
Date:   Wed, 16 Oct 2019 14:50:45 -0700
Message-Id: <20191016214844.418325456@linuxfoundation.org>
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From: Johan Hovold <johan@kernel.org>

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>

---
 drivers/usb/misc/legousbtower.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/usb/misc/legousbtower.c
+++ b/drivers/usb/misc/legousbtower.c
@@ -302,6 +302,7 @@ static inline void tower_delete (struct
 	kfree (dev->read_buffer);
 	kfree (dev->interrupt_in_buffer);
 	kfree (dev->interrupt_out_buffer);
+	usb_put_dev(dev->udev);
 	kfree (dev);
 }
 
@@ -818,7 +819,7 @@ static int tower_probe (struct usb_inter
 
 	mutex_init(&dev->lock);
 
-	dev->udev = udev;
+	dev->udev = usb_get_dev(udev);
 	dev->open_count = 0;
 	dev->disconnected = 0;