4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> commit 56897b217a1d0a91c9920cb418d6b3fe922f590a upstream. task A: task B: hci_uart_set_proto flush_to_ldisc - p->open(hu) -> h5_open //alloc h5 - receive_buf - set_bit HCI_UART_PROTO_READY - tty_port_default_receive_buf - hci_uart_register_dev - tty_ldisc_receive_buf - hci_uart_tty_receive - test_bit HCI_UART_PROTO_READY - h5_recv - clear_bit HCI_UART_PROTO_READY while() { - p->open(hu) -> h5_close //free h5 - h5_rx_3wire_hdr - h5_reset() //use-after-free } It could use ioctl to set hci uart proto, but there is a use-after-free issue when hci_uart_register_dev() fail in hci_uart_set_proto(), see stack above, fix this by setting HCI_UART_PROTO_READY bit only when hci_uart_register_dev() return success. Reported-by: syzbot+899a33dc0fa0dbaf06a6@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx> Reviewed-by: Jeremy Cline <jcline@xxxxxxxxxx> Signed-off-by: Marcel Holtmann <marcel@xxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/bluetooth/hci_ldisc.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/drivers/bluetooth/hci_ldisc.c +++ b/drivers/bluetooth/hci_ldisc.c @@ -696,14 +696,13 @@ static int hci_uart_set_proto(struct hci return -EPROTONOSUPPORT; hu->proto = p; - set_bit(HCI_UART_PROTO_READY, &hu->flags); err = hci_uart_register_dev(hu); if (err) { - clear_bit(HCI_UART_PROTO_READY, &hu->flags); return err; } + set_bit(HCI_UART_PROTO_READY, &hu->flags); return 0; }