This patch adds code to check HCI_UART_PROTO_READY flag before
accessing hci_uart->proto. It fixs the race condition in
hci_uart_tty_ioctl() between HCIUARTSETPROTO and HCIUARTGETPROTO.
This issue bug found by Yu Hao and Weiteng Chen:

BUG: general protection fault in hci_uart_tty_ioctl [1]

The information of C reproducer can also reference the link [2]

Reported-by: Yu Hao <yhao016@ucr.edu>
Closes: https://lore.kernel.org/all/CA+UBctC3p49aTgzbVgkSZ2+TQcqq4fPDO7yZitFT5uBPDeCO2g@mail.gmail.com/ [1]
Reported-by: Weiteng Chen <wchen130@ucr.edu>
Closes: https://lore.kernel.org/lkml/CA+UBctDPEvHdkHMwD340=n02rh+jNRJNNQ5LBZNA+Wm4Keh2ow@mail.gmail.com/T/ [2]
Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
---
 drivers/bluetooth/hci_ldisc.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index efdda2c3fce8..a76eb98c0047 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -770,7 +770,8 @@ static int hci_uart_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
 		break;
 
 	case HCIUARTGETPROTO:
-		if (test_bit(HCI_UART_PROTO_SET, &hu->flags))
+		if (test_bit(HCI_UART_PROTO_SET, &hu->flags) &&
+		    test_bit(HCI_UART_PROTO_READY, &hu->flags))
 			err = hu->proto->id;
 		else
 			err = -EUNATCH;
-- 
2.35.3

Hi Luiz Augusto von Dentz and all experts

Sorry for I send out a duplicate patch again. Just ignore this
duplicate patch, please.

Thanks!
Joey Lee

On Sat, Jul 15, 2023 at 12:08:54AM +0800, Lee, Chun-Yi wrote:
> This patch adds code to check HCI_UART_PROTO_READY flag before
> accessing hci_uart->proto. It fixs the race condition in
> hci_uart_tty_ioctl() between HCIUARTSETPROTO and HCIUARTGETPROTO.
> This issue bug found by Yu Hao and Weiteng Chen:
> 
> BUG: general protection fault in hci_uart_tty_ioctl [1]
> 
> The information of C reproducer can also reference the link [2]
> 
> Reported-by: Yu Hao <yhao016@ucr.edu>
> Closes: https://lore.kernel.org/all/CA+UBctC3p49aTgzbVgkSZ2+TQcqq4fPDO7yZitFT5uBPDeCO2g@mail.gmail.com/ [1]
> Reported-by: Weiteng Chen <wchen130@ucr.edu>
> Closes: https://lore.kernel.org/lkml/CA+UBctDPEvHdkHMwD340=n02rh+jNRJNNQ5LBZNA+Wm4Keh2ow@mail.gmail.com/T/ [2]
> Signed-off-by: "Lee, Chun-Yi" <jlee@suse.com>
> ---
>  drivers/bluetooth/hci_ldisc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
> index efdda2c3fce8..a76eb98c0047 100644
> --- a/drivers/bluetooth/hci_ldisc.c
> +++ b/drivers/bluetooth/hci_ldisc.c
> @@ -770,7 +770,8 @@ static int hci_uart_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
>  		break;
>  
>  	case HCIUARTGETPROTO:
> -		if (test_bit(HCI_UART_PROTO_SET, &hu->flags))
> +		if (test_bit(HCI_UART_PROTO_SET, &hu->flags) &&
> +		    test_bit(HCI_UART_PROTO_READY, &hu->flags))
>  			err = hu->proto->id;
>  		else
>  			err = -EUNATCH;
> -- 
> 2.35.3