[ALSA - driver 0000167]: alsamixer crashes system when snd-ioctl32 is loaded

[bugtrack@alsa-project.org]

A NOTE has been added to this issue.
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<https://bugtrack.alsa-project.org/alsa-bug/view.php?id=167> 
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Reported By:                bons78
Assigned To:                
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Project:                    ALSA - driver
Issue ID:                   167
Category:                   SPARC - cs4231
Reproducibility:            always
Severity:                   major
Priority:                   normal
Status:                     new
Distribution:               debian/unstable
Kernel Version:             linux-2.6.4+
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Date Submitted:             03-30-2004 00:02 CEST
Last Modified:              11-21-2004 22:46 CET
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Summary:                    alsamixer crashes system when snd-ioctl32 is loaded
Description: 
alsamixer crashes system hard when snd-ioctl32 is loaded.
System still responds to some sysrq commands (sync remount boot show) -
sysrq (term killall) has no effect.
There's no chance to do any other keyboard input. No logs, no traps, no
oops. Machine still responds to ping,(even port 22 stays open) but login
via ssh is not possible. 

alsamixer, of course, is useless without the ioctl32 wrapper loaded - but
does not crash the system then.
So I suspect a problem in the ioctl32 wrapper.



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----------------------------------------------------------------------
 eradicator - 11-21-04 21:36 
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ok... I tried the patched 2.6.9 snd-ioctl32 sources with my modified 2.6.7
kernel to the same freezing result...

----------------------------------------------------------------------
 sjoerd - 11-21-04 22:46 
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Ok. You apparently hit another problem. Just to very sure you could try my
patch on the sparclinux list on a vanilla 2.6.9..

 __attribute__((packed)) requests the kernel to pack a struct, which means
that there is no padding added. Normally a compiler can choose to add some
padding between the fields for better alignment, which can cause some
speedup.

The ioctl code encodes the size of the argument, thus the size the kernel
has and the size userspace has must be the same otherwise the ioctl is not
recognized. More important if the offset of the fields differ between user
and kernel space, nasty bugs can happen (which the reason for encoding the
size)

Using the packed attribute in kernel space and not in userspace can cause
a
size difference, that's why it was removed..

Issue History
Date Modified  Username       Field                    Change              
======================================================================
03-30-04 00:02 bons78         New Issue                                    
03-30-04 00:02 bons78         Distribution              => debian/unstable 
03-30-04 00:02 bons78         Kernel Version            => linux-2.6.4+    
04-13-04 19:41 tiwai          Note Added: 0000795                          
07-04-04 22:32 weeve          Note Added: 0001381                          
07-05-04 08:09 eradicator     Issue Monitored: eradicator                    
11-19-04 05:45 weeve          Note Added: 0002474                          
11-19-04 05:46 weeve          Issue Monitored: weeve                       
11-19-04 05:55 rlrevell       Note Added: 0002475                          
11-20-04 10:23 eradicator     Note Added: 0002478                          
11-20-04 11:14 eradicator     Note Added: 0002479                          
11-20-04 16:36 sjoerd         File Added: sparc-alsa-cvs.patch                  
 
11-20-04 16:36 sjoerd         Note Added: 0002480                          
11-20-04 18:15 sjoerd         Issue Monitored: sjoerd                      
11-21-04 03:05 eradicator     Note Added: 0002482                          
11-21-04 11:34 eradicator     File Added: alsa-driver-1.0.7.ioctl32.patch       
            
11-21-04 11:39 eradicator     Note Added: 0002485                          
11-21-04 11:49 eradicator     File Added: alsa-driver-1.0.7.ioctl32.patch       
            
11-21-04 11:50 eradicator     Note Added: 0002486                          
11-21-04 11:57 eradicator     Note Added: 0002487                          
11-21-04 12:54 sjoerd         Note Added: 0002488                          
11-21-04 17:44 sjoerd         Note Added: 0002489                          
11-21-04 21:26 eradicator     Note Added: 0002490                          
11-21-04 21:36 eradicator     Note Added: 0002491                          
11-21-04 22:46 sjoerd         Note Added: 0002492                          
======================================================================




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