[PATCH V3] Bluetooth: bfusb: Fix use-after-free and memory leak in device lifecycle

[Salah Triki <salah.triki@gmail.com>]

The driver stores a reference to the `usb_device` structure (`udev`)
in its private data (`data->udev`), which can persist beyond the
immediate context of the `bfusb_probe()` function.

Without proper reference count management, this can lead to two issues:

1. A `use-after-free` scenario if `udev` is accessed after its main
   reference count drops to zero (e.g., if the device is disconnected
   and the `data` structure is still active).
2. A `memory leak` if `udev`'s reference count is not properly
   decremented during driver disconnect, preventing the `usb_device`
   object from being freed.

To correctly manage the `udev` lifetime, explicitly increment its
reference count with `usb_get_dev(udev)` when storing it in the
driver's private data. Correspondingly, decrement the reference count
with `usb_put_dev(data->udev)` in the `bfusb_disconnect()` callback.

This ensures `udev` remains valid while referenced by the driver's
private data and is properly released when no longer needed.

Signed-off-by: Salah Triki <salah.triki@gmail.com>
Fixes: 9c724357f432d ("[Bluetooth] Code cleanup of the drivers source code")
Cc: stable@vger.kernel.org
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Cc: linux-bluetooth@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
Changes in v3:
    - Add tag Cc

Changes in v2:
    - Add tags Fixes and Cc
 drivers/bluetooth/bfusb.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/bluetooth/bfusb.c b/drivers/bluetooth/bfusb.c
index 8df310983bf6..f966bd8361b0 100644
--- a/drivers/bluetooth/bfusb.c
+++ b/drivers/bluetooth/bfusb.c
@@ -622,7 +622,7 @@ static int bfusb_probe(struct usb_interface *intf, const struct usb_device_id *i
 	if (!data)
 		return -ENOMEM;
 
-	data->udev = udev;
+	data->udev = usb_get_dev(udev);
 	data->bulk_in_ep    = bulk_in_ep->desc.bEndpointAddress;
 	data->bulk_out_ep   = bulk_out_ep->desc.bEndpointAddress;
 	data->bulk_pkt_size = le16_to_cpu(bulk_out_ep->desc.wMaxPacketSize);
@@ -701,6 +701,8 @@ static void bfusb_disconnect(struct usb_interface *intf)
 
 	usb_set_intfdata(intf, NULL);
 
+	usb_put_dev(data->udev);
+
 	bfusb_close(hdev);
 
 	hci_unregister_dev(hdev);
-- 
2.43.0