From: Jia-Hong Su Date: Sun, 18 Jan 2026 12:08:59 +0000 (+0800) Subject: Bluetooth: hci_uart: fix null-ptr-deref in hci_uart_write_work X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0c3cd7a0b862c37acbee6d9502107146cc944398;p=thirdparty%2Fkernel%2Fstable.git Bluetooth: hci_uart: fix null-ptr-deref in hci_uart_write_work hci_uart_set_proto() sets HCI_UART_PROTO_INIT before calling hci_uart_register_dev(), which calls proto->open() to initialize hu->priv. However, if a TTY write wakeup occurs during this window, hci_uart_tx_wakeup() may schedule write_work before hu->priv is initialized, leading to a NULL pointer dereference in hci_uart_write_work() when proto->dequeue() accesses hu->priv. The race condition is: CPU0 CPU1 ---- ---- hci_uart_set_proto() set_bit(HCI_UART_PROTO_INIT) hci_uart_register_dev() tty write wakeup hci_uart_tty_wakeup() hci_uart_tx_wakeup() schedule_work(&hu->write_work) proto->open(hu) // initializes hu->priv hci_uart_write_work() hci_uart_dequeue() proto->dequeue(hu) // accesses hu->priv (NULL!) Fix this by moving set_bit(HCI_UART_PROTO_INIT) after proto->open() succeeds, ensuring hu->priv is initialized before any work can be scheduled. Fixes: 5df5dafc171b ("Bluetooth: hci_uart: Fix another race during initialization") Link: https://lore.kernel.org/linux-bluetooth/6969764f.170a0220.2b9fc4.35a7@mx.google.com/ Signed-off-by: Jia-Hong Su Signed-off-by: Luiz Augusto von Dentz --- diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c index d0adae3267b41..2b28515de92c4 100644 --- a/drivers/bluetooth/hci_ldisc.c +++ b/drivers/bluetooth/hci_ldisc.c @@ -685,6 +685,8 @@ static int hci_uart_register_dev(struct hci_uart *hu) return err; } + set_bit(HCI_UART_PROTO_INIT, &hu->flags); + if (test_bit(HCI_UART_INIT_PENDING, &hu->hdev_flags)) return 0; @@ -712,8 +714,6 @@ static int hci_uart_set_proto(struct hci_uart *hu, int id) hu->proto = p; - set_bit(HCI_UART_PROTO_INIT, &hu->flags); - err = hci_uart_register_dev(hu); if (err) { return err;