Messages in this thread | | | Subject | Re: [PATCH v5] virtio-blk: Add validation for block size in config space | From | Max Gurtovoy <> | Date | Tue, 24 Aug 2021 01:31:10 +0300 |
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On 8/23/2021 3:13 PM, Michael S. Tsirkin wrote: > On Mon, Aug 23, 2021 at 01:45:31PM +0300, Max Gurtovoy wrote: >> It helpful if there is a justification for this. >> >> In this case, no such HW device exist and the only device that can cause >> this trouble today is user space VDUSE device that must be validated by the >> emulation VDUSE kernel driver. >> >> Otherwise, will can create 1000 commit like this in the virtio level (for >> example for each feature for each virtio device). > Yea, it's a lot of work but I don't think it's avoidable. > >>>>>>> And regardless of userspace device, we still need to fix it for other cases. >>>>>> which cases ? Do you know that there is a buggy HW we need to workaround ? >>>>>> >>>>> No, there isn't now. But this could be a potential attack surface if >>>>> the host doesn't trust the device. >>>> If the host doesn't trust a device, why it continues using it ? >>>> >>> IIUC this is the case for the encrypted VMs. >> what do you mean encrypted VM ? >> >> And how this small patch causes a VM to be 100% encryption supported ? >> >>>> Do you suggest we do these workarounds in all device drivers in the kernel ? >>>> >>> Isn't it the driver's job to validate some unreasonable configuration? >> The check should be in different layer. >> >> Virtio blk driver should not cover on some strange VDUSE stuff. > Yes I'm not convinced VDUSE is a valid use-case. I think that for > security and robustness it should validate data it gets from userspace > right there after reading it. > But I think this is useful for the virtio hardening thing. > https://lwn.net/Articles/865216/
I don't see how this change is assisting confidential computing.
Confidential computingtalks about encrypting guest memory from the host, and not adding some quirks to devices.
> > Yongji - I think the commit log should be much more explicit that > this is hardening. Otherwise people get confused and think this > needs a CVE or a backport for security. >
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