linux-kernel - [PATCH] Bluetooth: bcm203x: Fix use-after-free and memory leak in device lifecycle

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Message-ID: <aIR0ekNXjuLs6IWa@pc>
Date: Sat, 26 Jul 2025 07:23:54 +0100
From: Salah Triki <salah.triki@...il.com>
To: Marcel Holtmann <marcel@...tmann.org>,
	Luiz Augusto von Dentz <luiz.dentz@...il.com>,
	linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: salah.triki@...il.com
Subject: [PATCH] Bluetooth: bcm203x: Fix use-after-free and memory leak in
 device lifecycle

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 `bcm203x_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 `bcm203x_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@...il.com>
---
 drivers/bluetooth/bcm203x.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/bluetooth/bcm203x.c b/drivers/bluetooth/bcm203x.c
index c738ad0408cb..c91eaba33905 100644
--- a/drivers/bluetooth/bcm203x.c
+++ b/drivers/bluetooth/bcm203x.c
@@ -165,7 +165,7 @@ static int bcm203x_probe(struct usb_interface *intf, const struct usb_device_id
 	if (!data)
 		return -ENOMEM;

-	data->udev  = udev;
+	data->udev  = usb_get_dev(udev);
 	data->state = BCM203X_LOAD_MINIDRV;

 	data->urb = usb_alloc_urb(0, GFP_KERNEL);
@@ -243,6 +243,8 @@ static void bcm203x_disconnect(struct usb_interface *intf)

 	usb_set_intfdata(intf, NULL);

+	usb_put_dev(data->udev);
+
 	usb_free_urb(data->urb);
 	kfree(data->fw_data);
 	kfree(data->buffer);
-- 
2.43.0