Switching user freezes system

[DavidEG]

Just doing this my system freezes:

1. Click on the top right gear icon.
2. Select a different user account.

Login screen appears briefly, then black screen and the system is death:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000248
IP: [<ffffffffc0258eb2>] amdgpu_vm_grab_id+0x122/0x310 [amdgpu]
PGD 0
Oops: 0000 [#1] SMP
Modules linked in: ...
(See attached syslog for more)

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-22-generic 4.4.0-22.40
ProcVersionSignature: Ubuntu 4.4.0-22.40-generic 4.4.8
Uname: Linux 4.4.0-22-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: david 2739 F.... pulseaudio
 /dev/snd/controlC1: david 2739 F.... pulseaudio
CurrentDesktop: Unity
Date: Tue May 24 08:54:13 2016
HibernationDevice: RESUME=UUID=d225720a-fc40-49a3-9182-17d278d40460
InstallationDate: Installed on 2015-06-29 (329 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
MachineType: TOSHIBA SATELLITE S50-B
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-22-generic.efi.signed root=/dev/mapper/ubuntu--vg-root ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-4.4.0-22-generic N/A
 linux-backports-modules-4.4.0-22-generic N/A
 linux-firmware 1.157
SourcePackage: linux
UpgradeStatus: Upgraded to xenial on 2016-04-22 (31 days ago)
dmi.bios.date: 12/02/2014
dmi.bios.vendor: INSYDE Corp.
dmi.bios.version: 2.00
dmi.board.asset.tag: Type2 - Board Asset Tag
dmi.board.name: Type2 - Board Product Name1
dmi.board.vendor: Type2 - Board Vendor Name1
dmi.board.version: Type2 - Board Version
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: OEM Chassis ManuFacturer
dmi.chassis.version: OEM Chassis Version
dmi.modalias: dmi:bvnINSYDECorp.:bvr2.00:bd12/02/2014:svnTOSHIBA:pnSATELLITES50-B:pvrPSPQEE-00F00JEN:rvnType2-BoardVendorName1:rnType2-BoardProductName1:rvrType2-BoardVersion:cvnOEMChassisManuFacturer:ct10:cvrOEMChassisVersion:
dmi.product.name: SATELLITE S50-B
dmi.product.version: PSPQEE-00F00JEN
dmi.sys.vendor: TOSHIBA

[Brad Figg (brad-figg)]

This change was made by a bot.

[Joseph Salisbury (jsalisbury)]

Did this issue start happening after an update/upgrade? Was there a prior kernel version where you were not having this particular problem?

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.6 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.6-yakkety

[DavidEG (davideg)]

Since I've upgraded to 16.04 I've started to experience these system crashes:
* Sometimes, when I plug/unplug an external hdmi monitor.
* Sometimes, when I shutdown the machine.
Haven't reported those as they happen a bit randomly. I am not able to reproduce them at my will.

The one reported here, happens always. Before upgrading to 16.04 I only had one user so I don't know if the problem was there. That said, my feeling is that it is caused by the upgrade because the aforementioned issues.

Tested with the upstream kernel. The issue disappears (4.6.0-040600-generic #201605151930).

[penalvch (penalvch)]

DavidEG, the next step is to fully reverse commit bisect from kernel 4.4 to 4.6 in order to identify the last bad commit, followed immediately by the first good one. Once this good commit has been identified, it may be reviewed for backporting. Could you please do this following https://wiki.ubuntu.com/Kernel/KernelBisection#How_do_I_reverse_bisect_the_upstream_kernel.3F ?

Please note, finding adjacent kernel versions is not fully commit bisecting.

After the fix commit (not kernel version) has been identified, then please mark this report Status Confirmed.

Thank you for your understanding.

Helpful bug reporting tips:
https://wiki.ubuntu.com/ReportingBugs

[Launchpad Janitor (janitor)]

[Expired for linux (Ubuntu) because there has been no activity for 60 days.]

[L'Africain (lafricain79)]

Hi,
I have exactly the same problem with 14.04, with 16.04 it doens't freeze but I have just the icon (and not all) in the windows, without the text below it.
Same bug here : https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-intel/+bug/1247189 ?

[penalvch (penalvch)]

L'Africain, it will help immensely if you filed a new report with the Ubuntu repository kernel (not mainline/upstream) via a terminal:
ubuntu-bug linux

Please feel free to subscribe me to it.

For more on why this is helpful, please see https://wiki.ubuntu.com/ReportingBugs.

[L'Africain (lafricain79)]

Christopher what would you to know?
It's difficult for me to do a report because when the "freeze" happens I can do anything?? Maybe I can try with this file /var/log/kern.log?

[L'Africain (lafricain79)]

kern.log in attachment.

[penalvch (penalvch)]

L'Africain, please post future comments and attachments in the report you created (not here).

[L'Africain (lafricain79)]

I'm sorry I don't undestand what you ask me? Did you not to need about
the kern.log file?

2016-09-01 2:22 UTC+01:00, Christopher M. Penalver
<email address hidden>:
> L'Africain, please post future comments and attachments in the report
> you created (not here).
>
> ** Attachment removed: "kernel.log_before_freeze"
>
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1585081/+attachment/4731432/+files/kernel.log_before_freeze
>
> ** Attachment removed: "kernel.log_before_freeze"
>
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1585081/+attachment/4731431/+files/kernel.log_before_freeze
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1585081
>
> Title:
> Switching user freezes system
>
> Status in linux package in Ubuntu:
> Expired
>
> Bug description:
> Just doing this my system freezes:
>
> 1. Click on the top right gear icon.
> 2. Select a different user account.
>
> Login screen appears briefly, then black screen and the system is
> death:
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000248
> IP: [<ffffffffc0258eb2>] amdgpu_vm_grab_id+0x122/0x310 [amdgpu]
> PGD 0
> Oops: 0000 [#1] SMP
> Modules linked in: ...
> (See attached syslog for more)
>
> ProblemType: Bug
> DistroRelease: Ubuntu 16.04
> Package: linux-image-4.4.0-22-generic 4.4.0-22.40
> ProcVersionSignature: Ubuntu 4.4.0-22.40-generic 4.4.8
> Uname: Linux 4.4.0-22-generic x86_64
> ApportVersion: 2.20.1-0ubuntu2
> Architecture: amd64
> AudioDevicesInUse:
> USER PID ACCESS COMMAND
> /dev/snd/controlC0: david 2739 F.... pulseaudio
> /dev/snd/controlC1: david 2739 F.... pulseaudio
> CurrentDesktop: Unity
> Date: Tue May 24 08:54:13 2016
> HibernationDevice: RESUME=UUID=d225720a-fc40-49a3-9182-17d278d40460
> InstallationDate: Installed on 2015-06-29 (329 days ago)
> InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
> MachineType: TOSHIBA SATELLITE S50-B
> ProcFB: 0 inteldrmfb
> ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-22-generic.efi.signed
> root=/dev/mapper/ubuntu--vg-root ro quiet splash vt.handoff=7
> RelatedPackageVersions:
> linux-restricted-modules-4.4.0-22-generic N/A
> linux-backports-modules-4.4.0-22-generic N/A
> linux-firmware 1.157
> SourcePackage: linux
> UpgradeStatus: Upgraded to xenial on 2016-04-22 (31 days ago)
> dmi.bios.date: 12/02/2014
> dmi.bios.vendor: INSYDE Corp.
> dmi.bios.version: 2.00
> dmi.board.asset.tag: Type2 - Board Asset Tag
> dmi.board.name: Type2 - Board Product Name1
> dmi.board.vendor: Type2 - Board Vendor Name1
> dmi.board.version: Type2 - Board Version
> dmi.chassis.asset.tag: No Asset Tag
> dmi.chassis.type: 10
> dmi.chassis.vendor: OEM Chassis ManuFacturer
> dmi.chassis.version: OEM Chassis Version
> dmi.modalias:
> dmi:bvnINSYDECorp.:bvr2.00:bd12/02/2014:svnTOSHIBA:pnSATELLITES50-B:pvrPSPQEE-00F00JEN:rvnType2-BoardVendorName1:rnType2-BoardProductName1:rvrType2-BoardVersion:cvnOEMChassisManuFacturer:ct10:cvrOEMChassisVersion:
> dmi.produc...