Xorg crashed with SIGSEGV in XkbFreeInfo() when switching computer on a USB KVM switch

[Alex Mauer]

This happened when switching to this computer on a USB KVM switch.

#0 *__GI___libc_free (mem=0x202) at malloc.c:3709
 ar_ptr = <value optimized out>
 p = (mchunkptr) 0x1fa
#1 0x080aa301 in Xfree ()
No symbol table info available.
#2 0x0815ed02 in SrvXkbFreeClientMap ()
No symbol table info available.
#3 0x0815c80b in SrvXkbFreeKeyboard ()
No symbol table info available.
#4 0x0814e9cf in XkbFreeInfo ()

ProblemType: Crash
Architecture: i386
CrashCounter: 1
Date: Mon Jan 18 14:46:23 2010
DistroRelease: Ubuntu 10.04
ExecutablePath: /usr/bin/Xorg
MachineType: Dell Inc. Latitude D620
Package: xserver-xorg-core 2:1.7.3.902-1ubuntu8
PccardctlIdent:
 Socket 0:
   no product info available
PccardctlStatus:
 Socket 0:
   no card
ProcAttrCurrent: unconfined (enforce)
ProcCmdLine: root=/dev/mapper/system-root ro quiet splash
ProcCmdline: /usr/bin/X :0 -nr -verbose -auth /var/run/gdm/auth-for-gdm-MLIzPl/database -nolisten tcp vt7
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
 LANGUAGE=en_US:en
ProcVersionSignature: Ubuntu 2.6.32-10.14-generic
RelatedPackageVersions:
 xserver-xorg 1:7.5+1ubuntu1
 libgl1-mesa-glx 7.7-0ubuntu6
 libdrm2 2.4.17-0ubuntu1
 xserver-xorg-video-intel 2:2.9.1-1ubuntu1
 xserver-xorg-video-ati N/A
SegvAnalysis:
 Segfault happened at: 0x188e81 <free+49>: mov 0x4(%edx),%eax
 PC (0x00188e81) ok
 source "0x4(%edx)" (0x000001fe) not located in a known VMA region (needed readable region)!
 destination "%eax" ok
SegvReason: reading NULL VMA
Signal: 11
SourcePackage: xorg-server
StacktraceTop:
 realloc () from /lib/tls/i686/cmov/libc.so.6
 Xrealloc ()
 SrvXkbResizeKeyType ()
 ?? ()
 ?? ()
Tags: lucid
Title: Xorg crashed with SIGSEGV in realloc()
Uname: Linux 2.6.32-10-generic i686
UserGroups:

dmi.bios.date: 05/16/2008
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A10
dmi.board.name: 0TD761
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA10:bd05/16/2008:svnDellInc.:pnLatitudeD620:pvr:rvnDellInc.:rn0TD761:rvr:cvnDellInc.:ct8:cvr:
dmi.product.name: Latitude D620
dmi.sys.vendor: Dell Inc.
fglrx: Not loaded
glxinfo: Error: [Errno 2] No such file or directory
system:
 distro: Ubuntu
 architecture: i686kernel: 2.6.32-10-generic

[Apport retracing service (apport)]

StacktraceTop:
 *__GI___libc_realloc (oldmem=0x202, bytes=12) at malloc.c:3769
 Xrealloc ()
 SrvXkbResizeKeyType ()
 ?? ()
 ?? ()

[Bryce Harrington (bryce)]

Unfortunately the backtrace on this bug is a bit terse but looks like it is a fault in the Xkb keyboard code.

[Bryce Harrington (bryce)]

Hi Alex,

The terse backtrace doesn't give much to work with, and I don't think we can even send it upstream with what we've got. I have a KVM but it's not a USB kvm, and I've not reproduced this bug on it.

What you need to do is collect a more complete backtrace by hand. There are some guidelines available at http://wiki.ubuntu.com/X/Backtracing. Essentially you'll want to install the debug packages for any package with code showing up in the trace (usually xserver, plus drivers, and any assorted lib's that are referenced), and then run it through gdb.

Building xserver with --build-opts=nostrip,noopt or something like that might help if just installing the -dbg packages doesn't do it.

[Bryce Harrington (bryce)]

We're closing this bug since it is has been some time with no response from the original reporter. However, if the issue still exists please feel free to reopen with the requested information. Also, if you could, please test against the latest development version of Ubuntu, since this confirms the bug is one we may be able to pass upstream for help.