[X2Go-Dev] Segfault issue with x2goserver.

Nable 80 nable.maininbox at googlemail.com
Thu May 31 22:55:48 CEST 2012


Good daytime for everyone.

Since 2010 I've been using nxserver (freenx-0.7.3 + nxserver-3.4.0,
installed into /opt/NX ) on my Debian6 32-bit server ( currently
kernel 2.6.32-45, here is my /etc/apt/sources.list:
http://pastebin.ca/2156639 ).
I didn't use is for about 2-3 months and today I found that when I try
to connect to my server, it draws some initial graphics and then
connection interrupts.
In dmesg i see:
[4573539.498493] nxagent[5736]: segfault at 0 ip 080e3f03 sp bf9e6900
error 4 in nxagent[8048000+438000]
[4573581.591042] nxagent[6371]: segfault at 0 ip 080e3f03 sp bf9a1d90
error 4 in nxagent[8048000+438000]
... (same EIP each time)

I've thought that some update of X11 libs lead it to broke and
remembered that some some time ago in Debian repos appeared some NX
libs, so i've looked what depends on them. So, i've found x2goserver.
I've installed it ( as it described here:
http://wiki.x2go.org/doku.php/wiki:x2go-repository-debian ), installed
x2goclient on my Win32 notebook but when i try to connect, i see the
same thing: X client application (i use openbox+lxpanel there) do some
requests, in ~/.xsession-errors i can see smth like:
XIO:  fatal IO error 11 (Resource temporarily unavailable) on X server ":0.0"
      after 1070 requests (1070 known processed) with 0 events remaining.
and then no data comes to client. In dmesg i see:
[4578741.547603] x2goagent[18222]: segfault at 0 ip 080e87b1 sp
bfe1afd0 error 4 in nxagent[8048000+460000]
[4578947.507016] x2goagent[20046]: segfault at 0 ip 080e87b1 sp
bfbf80c0 error 4 in nxagent[8048000+460000]
... (same EIP each time)

I've used objdump and found that there program tries to read byte from
pointer (and doesn't check that it's not NULL) but there are no
debugging symbols, so i even don't catch what function is it.

Then i've tried installing x2goserver to my new Debian6 64bit server
(it's almost pure Debian installation) but when i try to connect to
it, the only application that works is fluxbox, if I try to start
anything like lxterminal, x2goagent fails at the code that looks very
similar to 32bit variant:
[794878.270330] x2goagent[29210]: segfault at 0 ip 00000000004a9bb0 sp
00007fff41ee6f60 error 4 in nxagent[400000+4f7000]
[795053.995418] x2goagent[30256]: segfault at 0 ip 00000000004a9bb0 sp
00007fff8ae42160 error 4 in nxagent[400000+4f7000]

If anyone cares, i'll try to send as much additional info as I can,
just tell what are you interested in. I can even try to debug it but i
still haven't understood how to build x2go utils from sources.



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