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

The driver was accessing its struct usb_interface 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: 66e3e591891d ("usb: Add driver for Altus Metrum ChaosKey device (v2)")
Cc: stable <stable@vger.kernel.org>     # 4.1
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191009153848.8664-3-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/misc/chaoskey.c b/drivers/usb/misc/chaoskey.c
index cf5828c..34e6cd6 100644 (file)
--- a/drivers/usb/misc/chaoskey.c
+++ b/drivers/usb/misc/chaoskey.c
@@ -98,6 +98,7 @@ static void chaoskey_free(struct chaoskey *dev)
                usb_free_urb(dev->urb);
                kfree(dev->name);
                kfree(dev->buf);
+               usb_put_intf(dev->interface);
                kfree(dev);
        }
 }
@@ -145,6 +146,8 @@ static int chaoskey_probe(struct usb_interface *interface,
        if (dev == NULL)
                goto out;
 
+       dev->interface = usb_get_intf(interface);
+
        dev->buf = kmalloc(size, GFP_KERNEL);
 
        if (dev->buf == NULL)
@@ -174,8 +177,6 @@ static int chaoskey_probe(struct usb_interface *interface,
                        goto out;
        }
 
-       dev->interface = interface;
-
        dev->in_ep = in_ep;
 
        if (le16_to_cpu(udev->descriptor.idVendor) != ALEA_VENDOR_ID)