Forwarding this bug report from Ubuntu reporter Brian Murray:
https://bugs.edge.launchpad.net/ubuntu/+source/xserver-xorg-video-ati/+bug/435559

[Problem]
Segfault in RADEONInit3DEngineMMIO.

src/radeon_commonfuncs.c:85 indicates perhaps this line is at fault?

        if (info->dri->pKernelDRMVersion->version_major < 2) {

Perhaps dri and pKernelDRMVersion need checks for NULL prior to being dereferenced?


[Original Bug Report]
I've had this occur semi-regularly and probably could make it happen again if more information is need.

This information also appears in dmesg after it happens:

[91522.826463] [drm:radeon_ib_schedule] *ERROR* radeon: couldn't schedule IB(2).
[91522.826467] [drm:radeon_cs_ioctl] *ERROR* Faild to schedule IB !
[91522.826526] [drm:radeon_ib_schedule] *ERROR* radeon: couldn't schedule IB(2).
[91522.826529] [drm:radeon_cs_ioctl] *ERROR* Faild to schedule IB !
[91582.827185] [drm:radeon_bo_move] *ERROR* CP is not ready use memcpy.

ProblemType: Crash
Architecture: amd64
Date: Wed Sep 23 15:32:32 2009
DistroRelease: Ubuntu 9.10
ExecutablePath: /usr/bin/Xorg
MachineType: Dell Inc. Dell DXP051
Package: xserver-xorg-core 2:1.6.3-1ubuntu6
ProcCmdLine: root=/dev/md1 ro radeon.modeset=1
ProcCmdline: /usr/bin/X :0 -br -verbose -auth /var/run/gdm/auth-for-gdm-DGBOB6/database -nolisten tcp vt7
ProcCwd: /etc/X11
ProcEnviron:
 LANG=en_US.UTF-8
 PATH=(custom, no user)
ProcVersionSignature: Ubuntu 2.6.31-10.35-generic
RelatedPackageVersions:
 xserver-xorg 1:7.4+3ubuntu5
 libgl1-mesa-glx 7.6.0~git20090817.7c422387-0ubuntu5
 libdrm2 2.4.13-1ubuntu1
 xserver-xorg-video-intel 2:2.8.1-1ubuntu1
 xserver-xorg-video-ati 1:6.12.99+git20090825.fc74e119-0ubuntu2
SegvAnalysis:
 Segfault happened at: 0x7f9907bf81ed <RADEONInit3DEngine+15901>: cmpl $0x1,(%rcx)
 PC (0x7f9907bf81ed) ok
 source "$0x1" ok
 destination "(%rcx)" (0x00000000) not located in a known VMA region (needed writable region)!
SegvReason: writing NULL VMA
Signal: 11
SourcePackage: xorg-server
StacktraceTop:
 RADEONInit3DEngineMMIO (pScrn=0xeb3a80)
 RADEONInit3DEngine (pScrn=0xeb3a80) at ../../src/radeon_accel.c:1129
 R300DisplayTexturedVideoMMIO (
 RADEONPutImageTextured (pScrn=0xeb3a80,
 ?? ()
Title: Xorg crashed with SIGSEGV in RADEONInit3DEngineMMIO()
Uname: Linux 2.6.31-10-generic x86_64
UserGroups:

dmi.bios.date: 10/28/2005
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A02
dmi.board.name: 0YC523
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 7
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA02:bd10/28/2005:svnDellInc.:pnDellDXP051:pvr:rvnDellInc.:rn0YC523:rvr:cvnDellInc.:ct7:cvr:
dmi.product.name: Dell DXP051
dmi.sys.vendor: Dell Inc.
fglrx: Not loaded
system:
 distro: Ubuntu
 architecture: x86_64kernel: 2.6.31-10-generic