Bluetooth: hci_ldisc: check HCI_UART_PROTO_READY flag in HCIUARTGETPROTO

This patch adds code to check HCI_UART_PROTO_READY flag before
accessing hci_uart->proto. It fixes 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>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index efdda2c..a76eb98 100644 (file)
--- 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;