[pulseaudio-discuss] How to close a session?

Haug Bürger pinus at dokom.net
Thu Dec 16 12:44:34 PST 2010

Colin Guthrie schrieb:
> 'Twas brillig, and Haug Bürger at 13/12/10 20:37 did gyre and gimble:
>> Colin Guthrie schrieb:
>>> 'Twas brillig, and Haug Bürger at 12/12/10 10:59 did gyre and gimble:
>>>> The leatest Ubuntu has a serious security bug caused by pulseaudio. If
>>>> you configure pammount to mount a crypted home directory it is not able
>>>> to unmount it because pulseaudio has files in use (.pulse/*). You can
>>>> not even kill the daemon because it is set to user session.
>>>> So, how can you stop the pulseaudio user session? In the hope that this
>>>> releases the files.
>>>> Is it really necessary for the deamon to lock the files that you can not
>>>> unmount or is this a bug?
>>> It's quite deliberate. PA has a timeout that prevents it from closing
>>> immediate. This means that if PA autospawns, it will stick around for a
>>> little while in case it's needed again (while startup is fairly quick,
>>> we do have to probe the hardware so it does take time). This is
>>> primarily for console applications rather than X11 however, as under X11
>>> a Session Manager module is loaded which keeps PA alive for the duration
>>> of the X session.
>>> You can make a change in daemon.conf to set exit-idle-time to 0. This
>>> should allow PA to exit when the X11 session exits.
>> This doesn't work. Probably because you might have another user session
>> with X11 active. This means PA is not closed and gdm can not close the
>> session properly.
> Do you mean you have two X11 sessions for the same user active? If so I
> don't understand why you'd want to unmount your $HOME in this case....
> If you do not mean that there are two sessions by the same user active
> can you please explain this statement some more as I don't fully
> appreciate what your are describing.
I'm not sure, I'm not an X11 expert. What I do is I change the user within
Ubuntu. That keeps all my application open an gives me a login for another
user. I have multiple desktops open. I think that means I have multiple
X11 sessions.
>> I don't care if PA still runs but why does it lock files in my home
>> directory?
> Well it uses a socket file to communicate with other processes. This
> file is typically stored in $TMPDIR which is often $HOME/tmp. I suspect
> it is this socket file that is causing you problems.
No, there were several files open in the .pulse directory open.
>> It is not even possible as root to shut down a user session. Gdm can not
>> even kill the user session. This makes PA a pain in the a...
> Not really sure what you mean here? Root can easily kill any PA process.
> Can you describe what you mean in more detail here?
Yes you can kill it and it pops up again immediately. And again it locks 
in my home directory. As root you can not shut down the PA session.
>> So, how can you stop the pulseaudio user session?
> A user can simply call "pulseaudio -k" will kill their PA session.
> However, depending on what other applications are still running, it may
> very well be autospawned again.
Yes but you have to be the user and the script runs as root. And root
wants to get rid of the user session.
> It would be very trivial to add a option to
> src/modules/x11/module-x11-xsmp.c in the kill_cb() that would shut down
> the PA daemon on X11 logout, but it is not currently done in order to
> ensure that multiple X11 sessions by one user are supported. I guess
> some smarts could allow for checking the loaded modules and only exit if
> no other x11-xmsp module instances exist.
I'm not sure what the term session means in the X11 context but,
usually you open a session A, maybe a session B and then you close e.g. A.
What has that to do with the user? Usually a session is something like a
handle and you use it to have multiple. If I logout one X11 session, why
should that close another session?
> I'm still not 100% sure why this whole thing is a problem tho'. I'm sure
> there is an easy way to kill all processes started by a user - this will
> certainly be especially true/easier when systemd handles user sessions:
I tried to use the gdm post session script to force unmount.
I tried to kill it and it pops up again immediately.

The problem is that PA prevents pam mount to unmount your crypted
home directory. It stays open, even after logout and there is no trigger
to close it. This makes all the crypting a useless.

All I want is to properly close a session previously opened at login. 
gdm nor myself are able to do that.
> http://0pointer.de/blog/projects/systemd-update-2.html
> "We now safely destroy all user session before going down. This is a
> feature long missing on Linux: since user processes were not killed
> until the very last moment the unhealthy situation that user code was
> running at a time where no other daemon was remaining was a normal part
> of shutdown."
That's nice but I do not shut down every time.

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