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

    Thanks,
    Jason

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