Re: User with no write permission on device can play audio

[Mayuresh <mayuresh%acm.org@localhost>]

On Sat, Apr 07, 2012 at 12:54:02AM +0530, Mayuresh wrote:
> I have set ownership of /dev/audio* and /dev/sound* /dev/hdaudio* to say
> user1 with no rwx permission for group and other. (Don't know which of
> audio*/hdaudio*/sound* matters. I have done it for all.)
> 
> Now as user2 - who has no permission of any kind on above devices, if I
> play something using mplayer, it says permission denied. However if as
> user2, I play something in firefox through flash plugin it plays the
> sound.

Understood that flash plugin runs via Linux emulation, which uses devices
under emul/linux/

To impose desired permissions for software that uses Linux emulation, I
need to set the permissions under emul/linu/dev/sound* etc.

Still wonder, isn't the physical device ultimately same? Can't setting the
permissions on /dev/sound* restrict the permissions even for emulated
devices? Does something run with setuid?

Mayuresh