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

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Message-ID: <20210113113017.GA28106@lst.de>
Date:   Wed, 13 Jan 2021 12:30:17 +0100
From:   Christoph Hellwig <hch@....de>
To:     Martin Radev <martin.b.radev@...il.com>
Cc:     konrad.wilk@...cle.com, hch@....de, m.szyprowski@...sung.com,
        robin.murphy@....com, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, joro@...tes.org,
        kirill.shutemov@...ux.intel.com, thomas.lendacky@....com,
        robert.buhren@...t.tu-berlin.de, file@...t.tu-berlin.de,
        mathias.morbitzer@...ec.fraunhofer.de,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org
Subject: Re: [PATCH] swiotlb: Validate bounce size in the sync/unmap path

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?