[PATCH v3 1/3] Bluetooth: btusb: Fix UAF of btusb_data by rx_work
From: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date: 2026-09-02 21:46:29
Subsystem:
bluetooth drivers, the rest · Maintainers:
Marcel Holtmann, Luiz Augusto von Dentz, Linus Torvalds
From: Luiz Augusto von Dentz <redacted>
btusb_close() and btusb_flush() cancel data->rx_work with the
asynchronous cancel_delayed_work(), so if btusb_rx_work() is already
running on another CPU it keeps running after the cancel returns.
btusb_disconnect() calls hci_unregister_dev(), which invokes
btusb_close(), and then frees the btusb_data. A still running
btusb_rx_work() then dereferences the freed data:
while ((skb = skb_dequeue(&data->acl_q)))
data->recv_acl(data->hdev, skb);
Use cancel_delayed_work_sync() instead. In btusb_close() the cancel also
has to happen after btusb_stop_traffic(), otherwise an URB completion
racing with the cancel can requeue the work right after it has been
waited for.
Fixes: 800fe5ec302e ("Bluetooth: btusb: Add support for queuing during polling interval")
Signed-off-by: Luiz Augusto von Dentz <redacted>
---
drivers/bluetooth/btusb.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index 03039ceaa77d..b42963417213 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c@@ -2096,18 +2096,24 @@ static int btusb_close(struct hci_dev *hdev) BT_DBG("%s", hdev->name); - cancel_delayed_work(&data->rx_work); cancel_work_sync(&data->work); cancel_work_sync(&data->waker); - skb_queue_purge(&data->acl_q); - clear_bit(BTUSB_ISOC_RUNNING, &data->flags); clear_bit(BTUSB_BULK_RUNNING, &data->flags); clear_bit(BTUSB_INTR_RUNNING, &data->flags); clear_bit(BTUSB_DIAG_RUNNING, &data->flags); btusb_stop_traffic(data); + + /* rx_work must only be canceled once the URBs that can rearm it are + * gone, and it must be canceled synchronously since btusb_disconnect() + * frees the btusb_data it dereferences right after hci_unregister_dev(). + */ + cancel_delayed_work_sync(&data->rx_work); + + skb_queue_purge(&data->acl_q); + btusb_free_frags(data); err = usb_autopm_get_interface(data->intf);
@@ -2133,7 +2139,7 @@ static int btusb_flush(struct hci_dev *hdev) BT_DBG("%s", hdev->name); - cancel_delayed_work(&data->rx_work); + cancel_delayed_work_sync(&data->rx_work); skb_queue_purge(&data->acl_q);
--
2.54.0