* Reshetova, Elena (elena.reshetova@xxxxxxxxx) wrote: > > On Wed, Jan 25, 2023 at 03:29:07PM +0000, Reshetova, Elena wrote: > > > Replying only to the not-so-far addressed points. > > > > > > > On Wed, Jan 25, 2023 at 12:28:13PM +0000, Reshetova, Elena wrote: > > > > > Hi Greg, > > > > <...> > > > > > > > 3) All the tools are open-source and everyone can start using them right > > away > > > > even > > > > > without any special HW (readme has description of what is needed). > > > > > Tools and documentation is here: > > > > > https://github.com/intel/ccc-linux-guest-hardening > > > > > > > > Again, as our documentation states, when you submit patches based on > > > > these tools, you HAVE TO document that. Otherwise we think you all are > > > > crazy and will get your patches rejected. You all know this, why ignore > > > > it? > > > > > > Sorry, I didn’t know that for every bug that is found in linux kernel when > > > we are submitting a fix that we have to list the way how it has been found. > > > We will fix this in the future submissions, but some bugs we have are found by > > > plain code audit, so 'human' is the tool. > > > > My problem with that statement is that by applying different threat > > model you "invent" bugs which didn't exist in a first place. > > > > For example, in this [1] latest submission, authors labeled correct > > behaviour as "bug". > > > > [1] https://lore.kernel.org/all/20230119170633.40944-1- > > alexander.shishkin@xxxxxxxxxxxxxxx/ > > Hm.. Does everyone think that when kernel dies with unhandled page fault > (such as in that case) or detection of a KASAN out of bounds violation (as it is in some > other cases we already have fixes or investigating) it represents a correct behavior even if > you expect that all your pci HW devices are trusted? What about an error in two > consequent pci reads? What about just some failure that results in erroneous input? I'm not sure you'll get general agreement on those answers for all devices and situations; I think for most devices for non-CoCo situations, then people are generally OK with a misbehaving PCI device causing a kernel crash, since most people are running without IOMMU anyway, a misbehaving device can cause otherwise undetectable chaos. I'd say: a) For CoCo, a guest (guaranteed) crash isn't a problem - CoCo doesn't guarantee forward progress or stop the hypervisor doing something truly stupid. b) For CoCo, information disclosure, or corruption IS a problem c) For non-CoCo some people might care about robustness of the kernel against a failing PCI device, but generally I think they worry about a fairly clean failure, even in the unexpected-hot unplug case. d) It's not clear to me what 'trust' means in terms of CoCo for a PCIe device; if it's a device that attests OK and we trust it is the device it says it is, do we give it freedom or are we still wary? Dave > Best Regards, > Elena. > -- Dr. David Alan Gilbert / dgilbert@xxxxxxxxxx / Manchester, UK
