Re: [PATCH v2 7/8] iommu: Export iommu_get_dma_domain

[Baolu Lu]

On 3/28/23 11:48 PM, Jacob Pan wrote:
> On Tue, 28 Mar 2023 14:04:15 +0800, Baolu Lu<baolu.lu@xxxxxxxxxxxxxxx>
> wrote:
>
> > 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.
> don't you have to unload the driver?

Yes, of cause.

Hence, the getting domain interfaces are only safe to be used in the
driver of the device.

Best regards,
baolu