Xorg crash

[Bronek Kozicki]

Steps to reproduce

1. setup a virtual machine with GPU pass-through to a nvidia Quadro card (nvidia only supports passthrough to Quadro cards). Nvidia also recommends that the passed-through card has its ROM disabled in VM configuration, i.e. <rom bar='off'/> . Attached an example of such VM.

2. install vanilla Xubuntu 18.04, do not enable auto-login

3. install nvidia drivers, e.g.
  $ sudo add-apt-repository ppa:graphics-drivers/ppa
  $ sudo apt-get install nvidia-driver-410

4. reboot (the screen may be black until the greeter appears)

5. login

6. lock the screen back to the greeter
  $ light-locker-command --lock

Now you have black screen and unresponsive keyboard, and also one more file in /var/crash . The only way to get to the greeter again is to run (from another session, e.g. ssh)
  $ sudo systemctl restart lightdm

... which will also kill all the sessions running under the login manger (including the one where we tried to lock the screen)

I've found that this only happens with stock xfwm4 version 4.12 . If I upgrade xfwm4 to version 4.13.1 (from ppa:xubuntu-dev/experimental) the screen lock works as expected.

So perhaps the problem is not with Xorg but with old xfwm4. I also tried other flavours of Ubuntu and IIRC also seen it in Lubuntu.

At a stretch this could be called security vulnerability, because with this bug there is no way to lock the screen, hence users will always leave their session unlocked (or must log off)

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: xorg 1:7.7+19ubuntu7.1
ProcVersionSignature: Ubuntu 4.15.0-45.48-generic 4.15.18
Uname: Linux 4.15.0-45-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
.proc.driver.nvidia.gpus.0000.06.00.0: Error: [Errno 21] Is a directory: '/proc/driver/nvidia/gpus/0000:06:00.0'
.proc.driver.nvidia.registry: Binary: ""
.proc.driver.nvidia.version:
 NVRM version: NVIDIA UNIX x86_64 Kernel Module 410.78 Sat Nov 10 22:09:04 CST 2018
 GCC version: gcc version 7.3.0 (Ubuntu 7.3.0-27ubuntu1~18.04)
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
BootLog:

CompositorRunning: None
Date: Mon Feb 11 09:14:54 2019
DistUpgraded: Fresh install
DistroCodename: bionic
DistroVariant: ubuntu
DkmsStatus: nvidia, 410.78, 4.15.0-45-generic, x86_64: installed
ExtraDebuggingInterest: Yes
GraphicsCard:
 NVIDIA Corporation GM204GL [Quadro M5000] [10de:13f0] (rev a1) (prog-if 00 [VGA controller])
   Subsystem: NVIDIA Corporation GM204GL [Quadro M5000] [10de:1152]
InstallationDate: Installed on 2019-02-10 (0 days ago)
InstallationMedia: Xubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
MachineType: QEMU Standard PC (Q35 + ICH9, 2009)
ProcEnviron:
 LANGUAGE=en_GB:en
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 SHELL=/bin/zsh
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.15.0-45-generic root=UUID=16524009-5b46-4f13-918c-0dee6cce40fe ro console=tty0 console=ttyS0,115200n8
SourcePackage: xorg
Symptom: display
Title: Xorg crash
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 02/06/2015
dmi.bios.vendor: EFI Development Kit II / OVMF
dmi.bios.version: 0.0.0
dmi.chassis.type: 1
dmi.chassis.vendor: QEMU
dmi.chassis.version: pc-q35-3.1
dmi.modalias: dmi:bvnEFIDevelopmentKitII/OVMF:bvr0.0.0:bd02/06/2015:svnQEMU:pnStandardPC(Q35+ICH9,2009):pvrpc-q35-3.1:cvnQEMU:ct1:cvrpc-q35-3.1:
dmi.product.name: Standard PC (Q35 + ICH9, 2009)
dmi.product.version: pc-q35-3.1
dmi.sys.vendor: QEMU
version.compiz: compiz N/A
version.libdrm2: libdrm2 2.4.95-1~18.04.1
version.libgl1-mesa-dri: libgl1-mesa-dri 18.2.2-0ubuntu1~18.04.2
version.libgl1-mesa-glx: libgl1-mesa-glx 18.2.2-0ubuntu1~18.04.2
version.nvidia-graphics-drivers: nvidia-graphics-drivers-* N/A
version.xserver-xorg-core: xserver-xorg-core 2:1.19.6-1ubuntu4.2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev N/A
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:18.0.1-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20171229-1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.15-2

[Daniel van Vugt (vanvugt)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It sounds like some part of the system has crashed. To help us find the cause of the crash please follow these steps:

1. Look in /var/crash for crash files and if found run:
    ubuntu-bug YOURFILE.crash
Then tell us the ID of the newly-created bug.

2. If step 1 failed then look at https://errors.ubuntu.com/user/ID where ID is the content of file /var/lib/whoopsie/whoopsie-id on the machine. Do you find any links to recent problems on that page? If so then please send the links to us.

3. If step 2 also failed then apply the workaround from bug 994921, reboot, reproduce the crash, and retry step 1.

Please take care to avoid attaching .crash files to bugs as we are unable to process them as file attachments. It would also be a security risk for yourself.

[Bronek Kozicki (bronek0)]

Submitted as #1816661 which seems to contain more information.

[Daniel van Vugt (vanvugt)]

Thanks. That shows this is a duplicate of bug 1543192.