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    SubjectRe: [PATCH v6 00/11] Fix BUG_ON in vfio_iommu_group_notifier()
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    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@nvidia.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

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