Re: [PATCH] vfio powerpc: implemented IOMMU driver for VFIO

[Alex Williamson]

On Wed, 2012-12-12 at 17:59 +1100, Alexey Kardashevskiy wrote:
> On 08/12/12 04:01, Alex Williamson wrote:
> >> +  case VFIO_IOMMU_MAP_DMA: {
> >> +          vfio_iommu_spapr_tce_dma_map param;
> >> +          struct iommu_table *tbl = container->tbl;
> >> +          enum dma_data_direction direction;
> >> +          unsigned long locked, lock_limit;
> >> +
> >> +          if (WARN_ON(!tbl))
> >> +                  return -ENXIO;
> >> +
> >> +          minsz = offsetofend(vfio_iommu_spapr_tce_dma_map, size);
> >> +
> >> +          if (copy_from_user(&param, (void __user *)arg, minsz))
> >> +                  return -EFAULT;
> >> +
> >> +          if (param.argsz < minsz)
> >> +                  return -EINVAL;
> >> +
> >> +          if ((param.flags & VFIO_DMA_MAP_FLAG_READ) &&
> >> +                          (param.flags & VFIO_DMA_MAP_FLAG_WRITE))
> >> +                  direction = DMA_BIDIRECTIONAL;
> >> +          else if (param.flags & VFIO_DMA_MAP_FLAG_READ)
> >> +                  direction = DMA_TO_DEVICE;
> >> +          else if (param.flags & VFIO_DMA_MAP_FLAG_WRITE)
> >> +                  direction = DMA_FROM_DEVICE;
> >> +          else
> >> +                  return -EINVAL;
> >
> > flags needs to be sanitized too.  Return EINVAL if any unknown bit is
> > set or else sloppy users may make it very difficult to make use of those
> > flag bits later.
> 
> 
> It already returns -EINVAL on any bit set except READ/WRITE, no?

No.  I could pass flags ~0 through there to get a read/write mapping and
cause you problems if you later want to define another bit.  Thanks,

Alex

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