Re: Re: [RFC PATCH 00/17] Add validation for used length

From: Yongji Xie
Date: Tue May 18 2021 - 04:30:01 EST


On Tue, May 18, 2021 at 7:40 AM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>
> On Mon, May 17, 2021 at 05:08:19PM +0800, Xie Yongji wrote:
> > Current virtio device drivers may trust the used length returned
> > in virtqueue_get_buf()/virtqueue_get_buf_ctx(). But the used length
> > might come from an untrusted device when VDUSE[1] is enabled. To
> > protect this case, this series tries to add validation for the
> > used length.
> >
> > Since many legacy devices will also set the used length incorrectly,
> > we did not add the validation unconditionally. Instead, we will do
> > the validation only when the device driver needs the used length.
> > A NULL len passed to virtqueue_get_buf()/virtqueue_get_buf_ctx()
> > will mean the used length is not needed by the device driver.
>
> Can we be more specific? Which drivers have problems when used len
> is incorrect? Maybe there's an easier way like validating the length
> in the driver ...
>

It's ok to me. But this means all future new drivers need to remember
to do the validation.

Now only virtio-net and virtio-console drivers have this problem. I
can send some patches to fix it.

Thanks,
Yongji