Re: [PATCH] swiotlb: Validate bounce size in the sync/unmap path

[Christoph Hellwig]

On Tue, Jan 12, 2021 at 04:07:29PM +0100, Martin Radev wrote:
> The size of the buffer being bounced is not checked if it happens
> to be larger than the size of the mapped buffer. Because the size
> can be controlled by a device, as it's the case with virtio devices,
> this can lead to memory corruption.
> 

I'm really worried about all these hodge podge hacks for not trusted
hypervisors in the I/O stack.  Instead of trying to harden protocols
that are fundamentally not designed for this, how about instead coming
up with a new paravirtualized I/O interface that is specifically
designed for use with an untrusted hypervisor from the start?