On Mon, Jul 07, 2014 at 12:04:09PM +0530, Amit Shah wrote: > On (Sun) 06 Jul 2014 [23:09:49], Kees Cook wrote: > > On Sun, Jul 6, 2014 at 10:51 PM, Amit Shah <amit.shah@xxxxxxxxxx> wrote: > > > On (Sun) 06 Jul 2014 [21:38:36], Kees Cook wrote: > > >> On Fri, Jul 4, 2014 at 10:34 PM, Amit Shah <amit.shah@xxxxxxxxxx> wrote: > > >> > The hwrng core asks for random data in the hwrng_register() call itself > > >> > from commit d9e7972619. This doesn't play well with virtio -- the > > >> > DRIVER_OK bit is only set by virtio core on a successful probe, and > > >> > we're not yet out of our probe routine when this call is made. This > > >> > causes the host to not acknowledge any requests we put in the virtqueue, > > >> > and the insmod or kernel boot process just waits for data to arrive from > > >> > the host, which never happens. > > >> > > >> Doesn't this mean that virtio-rng won't ever contribute entropy to the system? > > > > > > The initial randomness? Yes. But it'll start contributing entropy as > > > soon as it's used as the current source. > > > > How does that happen? I don't see an init function defined for it? > > I mean the regular usage; not the initial randomness patch that you > added. > > Initial randomness from virtio-rng currently won't be sourced. That's > no different from the way things were before your patch; and I can't > think of a way to make that happen for now. Yes, but this is a critical case. There are three common scenarios where long term keys are generated in entropy-deprived states: - boot to a Linux Install CD, encrypt system during install - first boot of a Linux-based embedded router, need SSL keys - first boot of a Linux VM, need SSH host keys We have the opportunity to make the third option suck less if we can get this right. > virtio's probe() has to finish before communication with the host can > start. If a virtio-rng device is the only hwrng in the system (very > likely in a guest), it's almost guaranteed that hwrng_init() won't be > called after hwrng_register() completes (as it would have already been > called and the virtio-rng device will have become the current_rng). Well, I'm confused. virtio-rng has no init function defined. So hwrng_init() will just return zero. I think the basic question is: Where in the virtio-rng driver does it execute init-style code? And why isn't that in an init function? Should we create a small init function that simply checks this DRIVER_OK bit? thx, Jason. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
