linux-kernel - Re: [RFC PATCH 00/12] Ion cleanup in preparation for moving out of staging

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Date:   Mon, 13 Mar 2017 14:59:23 -0700
From:   Laura Abbott <labbott@...hat.com>
To:     Rob Clark <robdclark@...il.com>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        devel@...verdev.osuosl.org, Rom Lemarchand <romlem@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Riley Andrews <riandrews@...roid.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Michal Hocko <mhocko@...nel.org>,
        "linaro-mm-sig@...ts.linaro.org" <linaro-mm-sig@...ts.linaro.org>,
        Linux MM <linux-mm@...ck.org>,
        Arve Hjønnevåg <arve@...roid.com>,
        Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>
Subject: Re: [RFC PATCH 00/12] Ion cleanup in preparation for moving out of
 staging

On 03/13/2017 02:29 PM, Rob Clark wrote:
> On Mon, Mar 13, 2017 at 5:09 PM, Laura Abbott <labbott@...hat.com> wrote:
>>> Hm, we might want to expose all the heaps as individual
>>> /dev/ion_$heapname nodes? Should we do this from the start, since
>>> we're massively revamping the uapi anyway (imo not needed, current
>>> state seems to work too)?
>>> -Daniel
>>>
>>
>> I thought about that. One advantage with separate /dev/ion_$heap
>> is that we don't have to worry about a limit of 32 possible
>> heaps per system (32-bit heap id allocation field). But dealing
>> with an ioctl seems easier than names. Userspace might be less
>> likely to hardcode random id numbers vs. names as well.
> 
> 
> other advantage, I think, is selinux (brought up elsewhere on this
> thread).. heaps at known fixed PAs are useful for certain sorts of
> attacks so being able to restrict access more easily seems like a good
> thing
> 
> BR,
> -R
> 

Some other kind of filtering (BPF/LSM/???) might work as well
(http://kernsec.org/files/lss2015/vanderstoep.pdf ?)

The fixed PA issue is a larger problem. We're never going to
be able to get away from "this heap must exist at address X"
problems but the location of CMA in general should be
randomized. I haven't actually come up with a good proposal
to this though.

I'd like for Ion to be a framework for memory allocation and
not security exploits. Hopefully this isn't a pipe dream.

Thanks,
Laura