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Bluetooth: hci_ldisc: Postpone HCI_UART_PROTO_READY bit set in hci_ua…

…rt_set_proto()

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@syzkaller.appspotmail.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Jeremy Cline <jcline@redhat.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
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Kefeng Wang authored and holtmann committed Feb 23, 2019
1 parent 4a67e5d commit 56897b217a1d0a91c9920cb418d6b3fe922f590a
Showing with 1 addition and 2 deletions.
  1. +1 −2 drivers/bluetooth/hci_ldisc.c
@@ -696,14 +696,13 @@ static int hci_uart_set_proto(struct hci_uart *hu, int id)
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;
}

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