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

Lu Baolu
2022-02-21T03:39:52Z

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