On 03/07/2018 12:58 PM, Greg KH wrote:
On Wed, Mar 07, 2018 at 12:23:56PM -0800, 
sathyanarayanan.kuppusw...@linux.intel.com wrote:
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppusw...@linux.intel.com>

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?
void usb_serial_generic_read_bulk_callback(struct urb *urb)

385         for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i) {
386                 if (urb == port->read_urbs[i])
387                         break;
388         }

In here, after this for loop is done (without any matching urb), i value will be equal to ARRAY_SIZE(port->read_urbs). So there is a possibility of usb_serial_generic_submit_read_urb() getting called with this invalid index.


thanks,

greg k-h
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--
Sathyanarayanan Kuppuswamy
Linux kernel developer

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