[pulseaudio-discuss] System mode & SHM

[Pali Rohár]

On Saturday 06 December 2014 23:20:10 Tanu Kaskinen wrote:
> On Sun, 2014-11-23 at 14:43 +0100, Pali Rohár wrote:
> > On Sunday 23 November 2014 09:25:46 David Henningsson wrote:
> > > On 2014-11-22 22:39, Pali Rohár wrote:
> > > > Hello,
> > > > 
> > > > it is possible to enable shared memory when pulseaudio
> > > > is stared in system mode?
> > > 
> > > Not without recompiling PulseAudio, the relevant code is
> > > in src/pulsecore/protocol_native.c, function
> > > command_auth:
> > > 
> > > #ifdef HAVE_CREDS
> > > 
> > >      if (do_shm) {
> > >      
> > >          /* Only enable SHM if both sides are owned by the
> > > 
> > > same * user. This is a security measure because otherwise
> > > data * private to the user might leak. */
> > > 
> > >          const pa_creds *creds;
> > >          if (!(creds = pa_pdispatch_creds(pd)) || getuid()
> > >          !=
> > > 
> > > creds->uid) do_shm = false;
> > > 
> > >      }
> > > 
> > > #endif
> > > 
> > > Maybe there's more stuff that needs to be changed as well,
> > > I don't know.
> > 
> > Ok, so what about adding parameter which force SHM support
> > if user/administrator/owner of system want to do that?
> 
> That sounds like a good idea.
> 
> It's a bit tricky to define the configuration syntax, though.
> We currently have the "enable-shm" option in daemon.conf, and
> that seems like the appropriate option to use here.
> Currently, "no" means "no" and "yes" means "yes, if shm is
> available and if we're not running in the system mode". We'd
> need a third option that would have the semantics of "yes, if
> shm is available". I don't know what the third option should
> be named. I'd want "yes" to refer to the new option, and
> introduce "user-mode-only" to refer to the current "yes", but
> that's not a good choice, because we should keep the old
> semantics attached to the old option values for compatibility
> reasons. I suggest
> "yes-also-in-system-mode" for the new option, but I really
> hope someone comes up with something better.

Ok, then what about adding new option "enable-shm-in-system" (or 
other name) which will be used for system mode and current option 
"enable-shm" will be used only for user mode?

-- 
Pali Rohár
pali.rohar at gmail.com
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