2019-02-23 04:20:25

by Kefeng Wang

Subject: [PATCH] Bluetooth: hci_ldisc: Postpone HCI_UART_PROTO_READY bit set in hci_uart_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: [email protected]
Signed-off-by: Kefeng Wang <[email protected]>
---
drivers/bluetooth/hci_ldisc.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 4918fefc4a6f..9562e72c1ae5 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/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;
}

--
2.20.1

2019-02-24 01:12:36

by Jeremy Cline

Subject: Re: [PATCH] Bluetooth: hci_ldisc: Postpone HCI_UART_PROTO_READY bit set in hci_uart_set_proto()

On Sat, Feb 23, 2019 at 12:33:27PM +0800, Kefeng Wang wrote:
> 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

I think commit 32a7b4cbe93b ("Bluetooth: hci_ldisc: Initialize hci_dev
before open()") in made this worse by inadvertently changing this from

- clear_bit HCI_UART_PROTO_READY
- p->close(hu) -> h5_close //free h5

to

- p->close(hu) -> h5_close //free h5
- clear_bit HCI_UART_PROTO_READY

because the close call got moved into hci_uart_register_dev(). I guess
that made the race window sufficiently wide to be easily reproducible,
but it looks like it was present even before that commit.

> - 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: [email protected]
> Signed-off-by: Kefeng Wang <[email protected]>
> ---
> drivers/bluetooth/hci_ldisc.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
> index 4918fefc4a6f..9562e72c1ae5 100644
> --- a/drivers/bluetooth/hci_ldisc.c
> +++ b/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;
> }
>
> --
> 2.20.1
>

For what it's worth:

Reviewed-by: Jeremy Cline <[email protected]>

2019-02-26 08:56:34

by Marcel Holtmann

Subject: Re: [PATCH] Bluetooth: hci_ldisc: Postpone HCI_UART_PROTO_READY bit set in hci_uart_set_proto()

Hi Kefeng,

> 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: [email protected]
> Signed-off-by: Kefeng Wang <[email protected]>
> ---
> drivers/bluetooth/hci_ldisc.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)

patch has been applied to bluetooth-next tree.

Regards

Marcel