Bug 1097801

Summary:	RHSA-2013-0669 breaks KDM w/ VNC
Product:	Red Hat Enterprise Linux 6	Reporter:	Brian Hinz <bphinz>
Component:	kdebase	Assignee:	Jan Grulich <jgrulich>
Status:	CLOSED WONTFIX	QA Contact:	Desktop QE <desktop-qa-list>
Severity:	medium	Docs Contact:
Priority:	unspecified
Version:	6.5	CC:	astrand, bphinz, david.knapik, jgrulich, rvokal, tpelka, twaugh
Target Milestone:	rc
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Hardware:	All
OS:	Linux
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Last Closed:	2017-12-06 10:44:42 UTC	Type:	Bug
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Description Brian Hinz 2014-05-14 14:45:13 UTC

Description of problem:

Changes to qt-x11 introduced by RHSA-2013-0669 appear to have broken KDM when used with vnc.  Xvnc exits abruptly after connecting with the following error message in /var/log/kdm:

X Error of failed request: BadAccess (attempt to access private resource denied)
  Major opcode of failed request:    131 (MIT-SHM)
  Minor opcode of failed request:    1 (X_ShmAttach)
  Serial number of failed request:  377
  Current serial number in output stream:  393

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

qt-x11-4.6.2-28.el6_5

How reproducible:

100%

Steps to Reproduce:
1. Configure system to use KDM as the display manager
2. Enable Xdmcp in kdmrc
3. Configure vncserver script to start Xvnc with options "-query localhost -once ..."
4. Start vncserver and connect.

Actual results:

Server disconnects and Xvnc process terminates.  Error messages are logged to /var/log/kdm.log

Expected results:

Xvnc does not terminate unexpectedly

Additional info:

Worked prior to qt updates.

Starting Xvnc with MIT-SHM disabled is the only workaround that I have found so far.

Additional confirmations of this behavior have been reported against openSUSE 13.1: https://bugzilla.novell.com/show_bug.cgi?id=807781

Comment 4 Than Ngo 2014-05-26 13:35:30 UTC

could you please attach the vncserver configuration so i can test?

thanks

Comment 5 Brian Hinz 2014-05-27 01:51:31 UTC

I don't use vncserver, but you can use the following config to test:

VNCSERVERARGS[1]="-query localhost -once -geometry 800x600 -depth 24"

Enable KDM as the display manager, enable XDMCP in KDM.  Startup vncserver and it should fail with the following message:

[bphinz@testhost-el6-x64 ~]$ sudo /sbin/service vncserver start
Starting VNC server: 1:bphinz 
WARNING: The first attempt to start Xvnc failed, possibly because the font
catalog is not properly configured.  Attempting to determine an appropriate
font path for this system and restart Xvnc using that font path ...
Could not start Xvnc.


Xvnc TigerVNC 1.1.0 - built Feb  4 2014 05:26:31
Copyright (C) 1999-2011 TigerVNC Team and many others (see README.txt)
See http://www.tigervnc.org for information on TigerVNC.
Underlying X server release 11300000, The X.Org Foundation

The above error message is misleading, it has nothing to do with the font path.  You can demonstrate this by just adding the "-extension MIT-SHM" option to VNCSERVERARGS and it should startup:

VNCSERVERARGS[1]="-query localhost -once -geometry 800x600 -depth 24 -extension MIT-SHM"

-brian

Comment 7 David Knapik 2015-05-06 20:21:54 UTC

I just tripped over this issue on RHEL6_U6

Let me know if you need additional details

Comment 12 Jan Kurik 2017-12-06 10:44:42 UTC

Red Hat Enterprise Linux 6 is in the Production 3 Phase. During the Production 3 Phase, Critical impact Security Advisories (RHSAs) and selected Urgent Priority Bug Fix Advisories (RHBAs) may be released as they become available.

The official life cycle policy can be reviewed here:

http://redhat.com/rhel/lifecycle

This issue does not meet the inclusion criteria for the Production 3 Phase and will be marked as CLOSED/WONTFIX. If this remains a critical requirement, please contact Red Hat Customer Support to request a re-evaluation of the issue, citing a clear business justification. Note that a strong business justification will be required for re-evaluation. Red Hat Customer Support can be contacted via the Red Hat Customer Portal at the following URL:

https://access.redhat.com/