Re: [PATCH] virt: Add vboxguest driver for Virtual Box Guest integration

[Arnd Bergmann]

On Wed, Oct 4, 2017 at 12:11 PM, Greg Kroah-Hartman
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> On Wed, Oct 04, 2017 at 11:32:23AM +0200, Hans de Goede wrote:
>> Hi,
>>
>> On 03-10-17 13:41, Hans de Goede wrote:
>>
>> <snip>
>>
>> > > > +#define CHECK_IOCTL_IN(req)                             \
>> > > > +do {                                         \
>> > > > +    if ((req)->Hdr.cbIn != (sizeof((req)->Hdr) + sizeof((req)->u.In)) || \
>> > > > +        (req)->Hdr.cbOut != sizeof((req)->Hdr))                 \
>> > > > +        return -EINVAL;                             \
>> > > > +} while (0)
>> > >
>> > > Make these things functions instead of macros.
>> >
>> > Turning these into functions is a good idea I will do so for v2.
>>
>> Correction, I forgot that the passed in "req" macro
>> argument has a different type with all the calls, so
>> these cannot be changed into functions because they
>> rely on sizeof on the specific type to do the size
>> checks.
>
> Don't we already have built-in checks for these types of things?  Surely
> we don't require each ioctl user in the kernel to do this by
> themselves...

No other driver uses this kind of header for the ioctl structures,
usually we just rely on the ioctl command number to encode the
size, or we copy a fixed length.

      Arnd