On Mon, Aug 23, 2021 at 08:40:30PM +0800, Yongji Xie wrote: > On Mon, Aug 23, 2021 at 8:13 PM Michael S. Tsirkin <mst@xxxxxxxxxx> 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/ > > > > 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. > > > > OK, do I need to send a v6? This patch seems to be already merged into > Linus's tree. > > Thanks, > Yongji No, it's a comment for the future - I assume you will keep adding this kind of validation in other places. -- MST
