Re: [PATCH v2] usb: devio: Add ioctl to disallow detaching kernel USB drivers.

From: BjÃrn Mork
Date: Mon Jan 25 2016 - 10:33:06 EST

Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> writes:
> On Mon, 25 Jan 2016, BjÃrn Mork wrote:
>> I don't feel much like an expert here, but I can certainly make up an
>> opinion anyway :)
>> Since 64bits kernels allow usb devio with interface numbers up to 63, I
>> guess you need __u64 to avoid limiting the range? Limiting will create
>> all sorts of followup problems, so it's definitely easiest to just go
>> with __u64.
> But the Linux USB stack only allows up to 32 interfaces (see
> include/linux/usb.h):
> /* this maximum is arbitrary */

Ah, I totally missed that. Thanks

> So there's no point using a 64-bit value.
> On the other hand, this value is supposed to be the same size as
> ps->ifclaimed, which is used as an argument to clear_bit(), set_bit(),
> and test_bit(). Those routines require unsigned long.

Maybe the input to these should be clamped to USB_MAXINTERFACES?