linux-kernel - Re: [RFT][PATCH v1 5/6] vfio/ccw: Add kmap_local

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Date:   Mon, 20 Jun 2022 12:39:56 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Nicolin Chen <nicolinc@...dia.com>, kwankhede@...dia.com,
        corbet@....net, hca@...ux.ibm.com, gor@...ux.ibm.com,
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Subject: Re: [RFT][PATCH v1 5/6] vfio/ccw: Add kmap_local_page() for memcpy

On Sun, Jun 19, 2022 at 11:32:07PM -0700, Christoph Hellwig wrote:

> > This helps because we now block io memory from ever getting into these
> > call paths. I'm pretty sure this is a serious security bug, but would
> > let the IBM folks remark as I don't know it all that well..
> 
> Prevent as in crash when trying to convert it to a page?

That or when calling memcpy() on an IO memory PFN that the guest
passed into the dma s/g list the ccw driver is processing.

Jason