ACK: [PATCH 1/1] USB: serial: io_ti: fix div-by-zero in set_termios

[Colin Ian King]

On 11/02/2019 17:40, Tyler Hicks wrote:
> From: Johan Hovold <johan at kernel.org>
> 
> Fix a division-by-zero in set_termios when debugging is enabled and a
> high-enough speed has been requested so that the divisor value becomes
> zero.
> 
> Instead of just fixing the offending debug statement, cap the baud rate
> at the base as a zero divisor value also appears to crash the firmware.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: stable <stable at vger.kernel.org>     # 2.6.12
> Reviewed-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> Signed-off-by: Johan Hovold <johan at kernel.org>
> 
> CVE-2017-18360
> 
> (cherry picked from commit 6aeb75e6adfaed16e58780309613a578fe1ee90b)
> Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
> ---
>  drivers/usb/serial/io_ti.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/serial/io_ti.c b/drivers/usb/serial/io_ti.c
> index 8c2b58ace70a..cbc1b3afca01 100644
> --- a/drivers/usb/serial/io_ti.c
> +++ b/drivers/usb/serial/io_ti.c
> @@ -2233,8 +2233,11 @@ static void change_port_settings(struct tty_struct *tty,
>  	if (!baud) {
>  		/* pick a default, any default... */
>  		baud = 9600;
> -	} else
> +	} else {
> +		/* Avoid a zero divisor. */
> +		baud = min(baud, 461550);
>  		tty_encode_baud_rate(tty, baud, baud);
> +	}
>  
>  	edge_port->baud_rate = baud;
>  	config->wBaudRate = (__u16)((461550L + baud/2) / baud);
> 

Clean cherry pick, looks OK to me.

Acked-by: Colin Ian King <colin.king at canonical.com>