linux-kernel - Re: [PATCH v6 00/11] Fix BUG_ON in vfio_iommu_group

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Date:   Mon, 21 Feb 2022 11:38:17 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     baolu.lu@...ux.intel.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Dan Williams <dan.j.williams@...el.com>, rafael@...nel.org,
        Diana Craciun <diana.craciun@....nxp.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Chaitanya Kulkarni <kch@...dia.com>,
        Stuart Yoder <stuyoder@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Li Yang <leoyang.li@....com>,
        Dmitry Osipenko <digetx@...il.com>,
        iommu@...ts.linux-foundation.org, linux-pci@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 00/11] Fix BUG_ON in vfio_iommu_group_notifier()

On 2/18/22 11:51 PM, Jason Gunthorpe wrote:
> On Fri, Feb 18, 2022 at 08:55:10AM +0800, Lu Baolu wrote:
>> Hi folks,
>>
>> The iommu group is the minimal isolation boundary for DMA. Devices in
>> a group can access each other's MMIO registers via peer to peer DMA
>> and also need share the same I/O address space.
>>
>> Once the I/O address space is assigned to user control it is no longer
>> available to the dma_map* API, which effectively makes the DMA API
>> non-working.
>>
>> Second, userspace can use DMA initiated by a device that it controls
>> to access the MMIO spaces of other devices in the group. This allows
>> userspace to indirectly attack any kernel owned device and it's driver.
> This series has changed quite a lot since v1 - but I couldn't spot
> anything wrong with this. It is a small incremental step and I think
> it is fine now, so
> 
> Reviewed-by: Jason Gunthorpe<jgg@...dia.com>
> 
> I hope you continue to work on the "Scrap iommu_attach/detach_group()
> interfaces" series and try to minimize all the special places testing
> against the default domain

Sure.

Best regards,
baolu