> From: Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Tuesday, March 28, 2023 2:04 PM
>
> On 3/28/23 7:21 AM, Jacob Pan wrote:
> > Devices that use ENQCMDS to submit work needs to retrieve its DMA
> > domain. It can then attach PASID to the DMA domain for shared mapping
> > (with RID) established by DMA API.
> >
> > Signed-off-by: Jacob Pan<jacob.jun.pan@xxxxxxxxxxxxxxx>
> > ---
> > drivers/iommu/iommu.c | 1 +
> > include/linux/iommu.h | 5 +++++
> > 2 files changed, 6 insertions(+)
> >
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index 10db680acaed..c51d343a75d2 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -2118,6 +2118,7 @@ struct iommu_domain
> *iommu_get_dma_domain(struct device *dev)
> > {
> > return dev->iommu_group->default_domain;
> > }
> > +EXPORT_SYMBOL_GPL(iommu_get_dma_domain);
>
> Directly exporting this function for external use seems unsafe. If the
> caller is the kernel driver for this device, it's fine because default
> domain remains unchanged during the life cycle of the driver. Otherwise,
> using this function may cause UAF. Keep in mind that group's default
> domain could be changed through sysfs.
>
> However, iommu_get_domain_for_dev() has already done so and has been
> exported. Maybe I'm worried too much. :-)
>
Agree. The kernel driver managing the device wants to get the current
domain of the device then iommu_get_domain_for_dev() is the right
interface. It knows the domain is the dma domain.
