Messages in this thread | | | Date | Tue, 31 May 2022 17:42:36 +0100 | Subject | Re: [PATCH 01/12] iommu/vt-d: Use iommu_get_domain_for_dev() in debugfs | From | Robin Murphy <> |
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On 2022-05-31 16:59, Jason Gunthorpe wrote: > 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'
It shouldn't be insurmountable to make this safe, it just needs a bit more than pfn_valid(), which can still return true off the ends of the memory map if they're not perfectly section-aligned, and for random reserved holes in the middle.
Robin.
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