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

Christian König
2021-02-25T10:34:51Z

Am 24.02.21 um 19:46 schrieb Jason Gunthorpe:
> 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.

That's a really good idea. MAP_PRIVATE and any driver mappings doesn't
really work at all.

Christian.

>
> Jason