linux-kernel - Re: [Linaro-mm-sig] Changing vma->vm_file in dma_buf_mmap()

Open Source and information security mailing list archives

Message-ID: <d82f08ee-2dec-18e8-fb06-d26f18ed777a@gmail.com>
Date:   Thu, 17 Sep 2020 14:24:29 +0200
From:   Christian König <ckoenig.leichtzumerken@...il.com>
To:     Jason Gunthorpe <jgg@...pe.ca>, christian.koenig@....com
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@...ts.linaro.org>, Linux MM <linux-mm@...ck.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <linux-media@...r.kernel.org>
Subject: Re: [Linaro-mm-sig] Changing vma->vm_file in dma_buf_mmap()

Am 17.09.20 um 14:18 schrieb Jason Gunthorpe:
> On Thu, Sep 17, 2020 at 02:03:48PM +0200, Christian König wrote:
>> Am 17.09.20 um 13:31 schrieb Jason Gunthorpe:
>>> On Thu, Sep 17, 2020 at 10:09:12AM +0200, Daniel Vetter wrote:
>>>
>>>> Yeah, but it doesn't work when forwarding from the drm chardev to the
>>>> dma-buf on the importer side, since you'd need a ton of different
>>>> address spaces. And you still rely on the core code picking up your
>>>> pgoff mangling, which feels about as risky to me as the vma file
>>>> pointer wrangling - if it's not consistently applied the reverse map
>>>> is toast and unmap_mapping_range doesn't work correctly for our needs.
>>> I would think the pgoff has to be translated at the same time the
>>> vm->vm_file is changed?
>>>
>>> The owner of the dma_buf should have one virtual address space and FD,
>>> all its dma bufs should be linked to it, and all pgoffs translated to
>>> that space.
>> Yeah, that is exactly like amdgpu is doing it.
>>
>> Going to document that somehow when I'm done with TTM cleanups.
> BTW, while people are looking at this, is there a way to go from a VMA
> to a dma_buf that owns it?

Only a driver specific one.

For TTM drivers vma->vm_private_data points to the buffer object. Not 
sure about the drivers using GEM only.

Why are you asking?

Regards,
Christian.

>
> Jason
> _______________________________________________
> Linaro-mm-sig mailing list
> Linaro-mm-sig@...ts.linaro.org
> https://lists.linaro.org/mailman/listinfo/linaro-mm-sig

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives