Bug 12382

Summary:	Timidity in alsa mode : Permission denied
Product:	Mageia	Reporter:	christian fischer <christian-maryse.fischer>
Component:	RPM Packages	Assignee:	Colin Guthrie <mageia>
Status:	RESOLVED FIXED	QA Contact:
Severity:	normal
Priority:	Normal	CC:	mageia, thierry.vignaud
Version:	Cauldron	Keywords:	NEEDINFO
Target Milestone:	---
Hardware:	x86_64
OS:	Linux
Whiteboard:
Source RPM:	systemd	CVE:
Status comment:

Description christian fischer 2014-01-21 17:07:12 CET

Description of problem:
Timidity in alsa mode can easily play music with rosegarden , but
from user:

$ timidity -iA -Os
Requested buffer size 32768, fragment size 8192
ALSA pcm 'default' set buffer size 32768, period size 8192 bytes
TiMidity starting in ALSA server mode
ALSA lib seq_hw.c:457:(snd_seq_hw_open) open /dev/snd/seq failed: Permission denied
error in snd_seq_open

from root timidity can play:

$ su -
password

[root@amdA4 ~]# timidity -iA -Os
Requested buffer size 32768, fragment size 8192
ALSA pcm 'default' set buffer size 32768, period size 8192 bytes
TiMidity starting in ALSA server mode
Opening sequencer port: 128:0 128:1 128:2 128:3

Version-Release number of selected component (if applicable):
mageia4 RC

How reproducible:


Steps to Reproduce:
1.
2.
3.


Reproducible: 

Steps to Reproduce:

Comment 1 Thierry Vignaud 2014-01-22 03:36:00 CET

Did you make the mistake to first run a sound app as root?
It can results in sound device no more usable by regular users....

Keywords: (none) => NEEDINFO
CC: (none) => mageia, thierry.vignaud

Comment 2 Colin Guthrie 2014-01-22 09:47:23 CET

Yeah the permissions on /dev/snd/seq are a bit of a problem.

It's not treated like other device nodes, but we *should* (eventually) have a nice way of dealing with this now in the form of the static nodes support in udev.

The /usr/lib/udev/rules.d/50-udev-default.rules file contains:

SUBSYSTEM=="sound", GROUP="audio", \
  OPTIONS+="static_node=snd/seq", OPTIONS+="static_node=snd/timer"


So both snd/seq and snd/timer *should* have ACLs.

On my system it appears only snd/timer does. Does that tally with you?

I've tried changing that rule to:

SUBSYSTEM=="sound", GROUP="audio", OPTIONS+="static_node=snd/seq"
SUBSYSTEM=="sound", GROUP="audio", OPTIONS+="static_node=snd/timer"

but it didn't help.

I'll have to check upstream as to why it's not applying to the snd/seq node.

Comment 3 Colin Guthrie 2014-01-22 10:02:19 CET

OK, so it seems the problem is somewhat simple.

The static nodes stuff in udev should be providing a mechanism to autoload the snd-seq module. Sadly users can only trigger this if they have access to the node and this is where a chicken and egg scenario comes in. The ACL is only applied if the module is loaded, so users cannot trigger the autoload to give themselves permission.

This is ultimately a bug in the static nodes code.

A simply work around in the mean time is adding snd-seq to a *.conf file in /etc/modules-load.d/

Assignee: bugsquad => mageia
Source RPM: timidity ++ ? => systemd

Comment 4 Colin Guthrie 2014-01-22 11:03:42 CET

Actually I lied above. The rule change DOES work, but I spoke to Kay upstream and he's now pushed a fix. Testing that shortly.

Comment 5 Colin Guthrie 2014-01-22 11:11:53 CET

Yup, that works.

Should be fixed in next systemd.

Comment 6 Colin Guthrie 2014-01-25 12:36:50 CET

Freeze push requested.

Status: NEW => RESOLVED
Resolution: (none) => FIXED