Messages in this thread | | | Date | Wed, 4 Oct 2017 16:34:25 +0200 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH] virt: Add vboxguest driver for Virtual Box Guest integration |
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On Wed, Oct 04, 2017 at 12:40:54PM +0200, Hans de Goede wrote: > Hi, > > On 04-10-17 12:30, Greg Kroah-Hartman wrote: > > On Wed, Oct 04, 2017 at 12:23:41PM +0200, Arnd Bergmann wrote: > > > On Wed, Oct 4, 2017 at 12:11 PM, Greg Kroah-Hartman > > > <gregkh@linuxfoundation.org> 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. > > > > Then why can't we do the same thing here as well? > > VirtualBox uses the same ioctl interface for the guest-additions userspace > parts on all supported platforms and not all platforms support encoding > the size in the ioctl number, so all the ioctl data structs have a header > with the in and out sizes in there, these macros check that header. > > As mentioned during the RFC discussions changing the ioctl interface > is going to be troublesome to do because we want to be ABI compatible > with the kernel module shipped with the guest additions. > > Having 2 separate guest additions builds, one for running with the out > of tree driver (which eventually should go away I hope, but certainly not > soon) and another build for the mainline version of the vboxguest driver > is not supportable. > > I'm confident that if we find issues during the review process, which > have security implications, or where behavior is not clearly specified, > that we can get VirtualBox upstream to fix the API for that, but outright > re-designing the API is not really an option I believe. > > As for these specific macros to check the ioctl data struct header, > if these are considered a problem I can simply write out the code in > the few places where this macro is called.
Ok, that makes a bit more sense, let's see what your next round of patches look like, we can take it from there :)
thanks,
greg k-h
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