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Date:   Wed, 13 Jan 2021 12:30:17 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Martin Radev <martin.b.radev@gmail.com>
Cc:     konrad.wilk@oracle.com, hch@lst.de, m.szyprowski@samsung.com,
        robin.murphy@arm.com, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, joro@8bytes.org,
        kirill.shutemov@linux.intel.com, thomas.lendacky@amd.com,
        robert.buhren@sect.tu-berlin.de, file@sect.tu-berlin.de,
        mathias.morbitzer@aisec.fraunhofer.de,
        virtualization@lists.linux-foundation.org, kvm@vger.kernel.org
Subject: Re: [PATCH] swiotlb: Validate bounce size in the sync/unmap path
Message-ID: <20210113113017.GA28106@lst.de>
References: <X/27MSbfDGCY9WZu@martin>
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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?