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

[sathyanarayanan kuppuswamy]

On 03/08/2018 12:54 AM, Oliver Neukum wrote:
> Am Mittwoch, den 07.03.2018, 13:41 -0800 schrieb sathyanarayanan
> kuppuswamy       :
> > On 03/07/2018 12:58 PM, Greg KH wrote:
> > > 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)
> >
> > 385ÂÂÂÂÂÂÂÂ for (i = 0; i < ARRAY_SIZE(port->read_urbs); ++i) {
> > 386ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ if (urb == port->read_urbs[i])
> > 387ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ break;
> > 388ÂÂÂÂÂÂÂÂ }
> >
> > 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.
> If this happens the function was called for a stray URB.
> Your check comes to late. We have called set_bit with an invalid index
> and other shit.
> We definitely do not just want to return an error in that case.
In that case do you think we should use some WARN_ON() for invalid index 
in usb_serial_generic_read_bulk_callback()?
> 	Regards
> 		Oliver
>
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--
Sathyanarayanan Kuppuswamy
Linux kernel developer