linux-kernel - Re: [RFC PATCH] ALSA: core: Add DMA share buffer support

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Message-ID: <20190121124053.GA12679@sirena.org.uk>
Date:   Mon, 21 Jan 2019 12:40:53 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
        arnd@...db.de, keescook@...omium.org, bgoswami@...eaurora.org,
        sr@...x.de, gustavo@...eddedor.com, philburk@...gle.com,
        willy@...radead.org, mchehab+samsung@...nel.org, sboyd@...nel.org,
        vkoul@...nel.org, Baolin Wang <baolin.wang@...aro.org>,
        daniel.thompson@...aro.org, leo.yan@...aro.org,
        mathieu.poirier@...aro.org, srinivas.kandagatla@...aro.org,
        anna-maria@...utronix.de, corbet@....net, jmiller@...erware.com,
        ckeepax@...nsource.wolfsonmicro.com, joe@...ches.com,
        o-takashi@...amocchi.jp, colyli@...e.de,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] ALSA: core: Add DMA share buffer support

On Fri, Jan 18, 2019 at 08:39:32PM +0100, Takashi Iwai wrote:
> Mark Brown wrote:

> > > multiple tasks). I would probably go in this way and add more extended
> > > permission control for the PCM device, so permissions can be restricted
> > > for the passed descriptor to the producer or the consumer task. In this

> > One concern I have with doing some ALSA-specific custom permissions
> > thing is integration with frameworks like SELinux (they'd presumably
> > need to learn about the ALSA specific stuff to manage it).  It also

> Well, I wonder what makes it more difficult by the approach Jaroslav
> suggested.  With O_APPEND, you can just call mmap() normally, and
> that's all. What's the merit of dma-buf approach wrt the security?

It was the bit about adding more extended permission control that I was
worried about there, not the initial O_APPEND bit.  Indeed the O_APPEND
bit sounds like it might also work from the base buffer sharing point of
view, I have to confess I'd not heard of that feature before (it didn't
come up in the discussion when Eric raised this in Prague).

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