[alsa-devel] [PATCH 0/2] ALSA: pcm: implement the anonymous dup v3

[Mark Brown]

On Wed, Jan 30, 2019 at 01:41:37PM +0100, Jaroslav Kysela wrote:
> This patchset contains the anonymous dup implementation with permissions
> checking for the ALSA's PCM interface in kernel to enable the restricted
> DMA sound buffer sharing for the restricted tasks.
> 
> The code was tested through qemu and it seems to be pretty stable.
> 
> The initial tinyalsa implementation can be found here:
> 
>   https://github.com/perexg/tinyalsa/commits/anondup
> 
> The filtering might be refined. It depends on the real requirements.
> Perhaps, we may create more ioctl groups. Any comments are more than
> welcome.

My understanding based on some off-list discussion is that the Android
security people are going to see anything that involves passing more
than a block of memory (and in particular anything that gives access to
the sound APIs) as a problem.  That's obviously going to be an issue for
anything O_APPEND based.  My understanding is that this is fundamentally
a risk mitigation thing - by not having any of the sound kernel
interfaces available to the applications affected there's no possibility
that any problems in the sound code can cause security issues.
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