Re: [PATCH 01/12] iommu/vt-d: Use iommu_get_domain_for_dev() in debugfs

Jason Gunthorpe via iommu
2022-05-31T15:59:15Z

On Tue, May 31, 2022 at 02:52:28PM +0100, Robin Murphy wrote:

> > +                break;
> > +            pgtable_walk_level(m, phys_to_virt(phys_addr),
>
> Also, obligatory reminder that pfn_valid() only means that pfn_to_page()
> gets you a valid struct page. Whether that page is direct-mapped kernel
> memory or not is a different matter.

Even though this is debugfs, if the operation is sketchy like that and
can theortically crash the kernel the driver should test capabilities,
CAP_SYS_RAWIO or something may be appropriate. I don't think we have a
better cap for 'userspace may crash the kernel'

Jason