Re: [Linaro-mm-sig] [PATCH 1/2] dma-buf: Require VM_PFNMAP vma for mmap

Jason Gunthorpe
2021-02-24T18:48:08Z

On Wed, Feb 24, 2021 at 09:45:51AM +0100, Daniel Vetter wrote:

> Hm I figured everyone just uses MAP_SHARED for buffer objects since
> COW really makes absolutely no sense. How would we enforce this?

In RDMA we test

drivers/infiniband/core/ib_core_uverbs.c: if (!(vma->vm_flags & VM_SHARED))

During mmap to reject use of MAP_PRIVATE on BAR pages.

Jason