Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
iommupt: Check for missing PAGE_SIZE in the pgsize_bitmap
Sashiko pointed out that the driver could drop PAGE_SIZE from the pgsize_bitmap. That is technically allowed but nothing does it, and such an iommu_domain would not be used with the DMA API today.
Still, it is against the design and it is trivial to fix up. Lift the PT_WARN_ON to the if branch and just skip the fast path.