On Sun, Jan 12, 2025 at 09:55:58AM +0000, Qasim Ijaz wrote:
> This patch addresses a null-ptr-deref in qt2_process_read_urb() due to
> an incorrect bounds check in the following:
>
> ""
> if (newport > serial->num_ports) {
> dev_err(&port->dev,
> "%s - port change to invalid port: %i\n",
> __func__, newport);
> break;
> }
> ""
>
> The condition doesn't account for the valid range of the serial->port
> buffer, which is from 0 to serial->num_ports - 1. When newport is equal
> to serial->num_ports, the assignment of "port" in the
> following code is out-of-bounds and NULL:
>
> ""
> serial_priv->current_port = newport;
> port = serial->port[serial_priv->current_port];
>
> ""
>
> The fix checks if newport is greater than or equal to serial->num_ports
> indicating it is out-of-bounds.
>
> Reported-by: syzbot <syzbot+506479ebf12fe435d01a@xxxxxxxxxxxxxxxxxxxxxxxxx>
> Closes: https://syzkaller.appspot.com/bug?extid=506479ebf12fe435d01a
Oh wow, syzbot is now starting to fuzz random USB devices? And this is
the only thing it found for this device? That's not all that bad, I
expected much worse.
> Signed-off-by: Qasim Ijaz <qasdev00@xxxxxxxxx>
> ---
> drivers/usb/serial/quatech2.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/usb/serial/quatech2.c b/drivers/usb/serial/quatech2.c
> index a317bdbd00ad..72fe83a6c978 100644
> --- a/drivers/usb/serial/quatech2.c
> +++ b/drivers/usb/serial/quatech2.c
> @@ -503,7 +503,7 @@ static void qt2_process_read_urb(struct urb *urb)
>
> newport = *(ch + 3);
>
> - if (newport > serial->num_ports) {
> + if (newport >= serial->num_ports) {
> dev_err(&port->dev,
> "%s - port change to invalid port: %i\n",
> __func__, newport);
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
