Bug#494167: xvfb: crashes due to dbus/hal problems

[Brad King <brad.king@kitware.com>]

Package: xvfb
Version: 2:1.4.2-2
Severity: important

I run tests of a project that needs an X server on a nightly basis.  For
years I've been running them off-screen using Xvfb.  I start an
instance:

  Xvfb :52 -screen 0 1024x768x24 -fbdir /tmp/xvfb.52 -ac

and then run tests with "DISPLAY=:52".  Recently I updated my debian
testing system and the server has started crashing regularly after a few
hundred tests have run.  I tried building the version of the code being
tested to a time before this problem started but it didn't help.
Unfortunately I've been unable to reproduce the crash except by running
all the tests (and eventually one crashes Xvfb but which one is not
repeatable).  However, I've localized the problem somewhat.

The Xvfb process reports a bunch of these messages (about 1 per test):

----------------------------------------------------------------------
FreeFontPath: FPE "/usr/share/fonts/X11/misc" refcount is 2, should be 1; fixing.
----------------------------------------------------------------------

Later it reports a few messages of this form:

----------------------------------------------------------------------
[config/hal] couldn't initialise context: org.freedesktop.DBus.Error.LimitsExceeded (Connection ":1.20" is not allowed to add more match rules (increase limits in configuration file if required))
----------------------------------------------------------------------

and then crashes.  If I stop the dbus daemon (/etc/init.d/dbus stop) the
crash does not occur.  I found some discussion about this error here:

http://www.nabble.com/org.freedesktop.DBus.Error.LimitsExceeded-td17000158.html

but didn't see much about fixing it.

I used "apt-get source" for dbus and hal to build them with debug
symbols and install them into my home directory.  Using LD_LIBRARY_PATH
I ran the system's Xvfb installation with my own dbus and hal libraries.
Of course it stopped crashing.  Then I discovered that if I use
--localstatedir=/var when building dbus it crashes again.  I'm pretty
sure that's because it needs to see the file

  /var/run/dbus/system_bus_socket

Running with debug builds of the dbus and hal libraries let me get a
partial backtrace for the segfault:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x2b8f43d80610 (LWP 1266)]
0x0000000000000020 in ?? ()
(gdb) where
#0  0x0000000000000020 in ?? ()
#1  0x00002b8f428a8014 in filter_func (connection=0xb9abe0, message=0xb9b060, user_data=0xd2d2b0) at libhal.c:1190
#2  0x00002b8f42ac348b in dbus_connection_dispatch (connection=0xb9abe0) at dbus-connection.c:4385
#3  0x00002b8f42ac3843 in _dbus_connection_read_write_dispatch (connection=0xb9abe0, timeout_milliseconds=0, dispatch=<value optimized out>) at dbus-connection.c:3414
#4  0x00000000004bb0ab in ?? ()

The line "libhal.c:1190" is inside this a condition and loop:

if (dbus_message_is_signal (message, "org.freedesktop.Hal.Device", "PropertyModified"))
  if (ctx->device_property_modified != NULL) {
    ...
    for (i = 0; i < num_modifications; i++) {
      ...
	ctx->device_property_modified (ctx,  // line 1190
				       object_path,
				       key,
				       removed,
				       added);

It looks like the device_property_modified pointer-to-function is bad.

Please let me know if you need more information.

FYI, I originally posted the problem to debian-user asking to what
package I should report this bug:

  http://lists.debian.org/debian-user/2008/07/msg02915.html

but I have not heard back for a week so I'm guessing xvfb.

-- System Information:
Debian Release: lenny/sid
  APT prefers testing
  APT policy: (989, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 2.6.22-2-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages xvfb depends on:
ii  libc6                         2.7-10     GNU C Library: Shared libraries
ii  libdbus-1-3                   1.2.1-2    simple interprocess messaging syst
ii  libfontenc1                   1:1.0.4-3  X11 font encoding library
ii  libhal1                       0.5.11-2   Hardware Abstraction Layer - share
ii  libpixman-1-0                 0.10.0-2   pixel-manipulation library for X a
ii  libxau6                       1:1.0.3-3  X11 authorisation library
ii  libxdmcp6                     1:1.0.2-3  X11 Display Manager Control Protoc
ii  libxfont1                     1:1.3.3-1  X11 font rasterisation library
ii  x11-common                    1:7.3+14   X Window System (X.Org) infrastruc

Versions of packages xvfb recommends:
ii  xbase-clients                 1:7.3+14   miscellaneous X clients - metapack
ii  xfonts-base                   1:1.0.0-5  standard fonts for X

xvfb suggests no packages.

-- no debconf information