Re: [PATCH v1 1/1] USB: serial: Add boundry check for read_urbs array access

From: Greg KH
Date: Wed Mar 07 2018 - 15:58:46 EST


On Wed, Mar 07, 2018 at 12:23:56PM -0800, sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx wrote:
> From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
>
> In usb_serial_generic_submit_read_urb() function we are accessing the
> port->read_urbs array without any boundry checks. This might lead to
> kernel panic when index value goes above array length.
>
> One posible call path for this issue is,
>
> usb_serial_generic_read_bulk_callback()
> {
> ...
> if (!port->throttled) {
> usb_serial_generic_submit_read_urb(port, i, GFP_ATOMIC);
> ...
> }

How does i ever get to be greater than the array size here in this
function? It directly came from looking in that array in the first
place :)

So I don't see why your check is needed, what other code path would ever
call this function in a way that the bounds check would be needed?

thanks,

greg k-h