BUG: unable to handle kernel NULL pointer dereference at (null); RIP: 0010:[<ffffffff81313532>] [<ffffffff81313532>] strlen+0x2/0x20

[Eoin]

Dual boot Ubuntu 12.04 / Win7 SP1 Dell Optiplex 990 computer. The following problem is repeatable every time and occurs on multiple machines. When running update-grub the terminal displays:

dtc-admin@DTC141:~$ sudo update-grub
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-3.2.0-23-generic
Found initrd image: /boot/initrd.img-3.2.0-23-generic
Found memtest86+ image: /boot/memtest86+.bin
/usr/lib/os-probes/50mounted-tests: line 92: 6350 Killed grub-mount "$partition" "$tmpmnt" 2> /dev/null
/usr/lib/os-probes/50mounted-tests: line 92: 6370 Killed grub-mount "$partition" "$tmpmnt" 2> /dev/null
done

update-grub doees not generate entries for the win7 partition so the system can no longer be booted into that OS.
/var/log/syslog reports:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1027110/+attachment/3229988/+files/syslog

grub2-common version is:
grub2-common:
  Installed: 1.99-21ubuntu3.1
  Candidate: 1.99-21ubuntu3.1
  Version table:
 *** 1.99-21ubuntu3.1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ precise-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     1.99-21ubuntu3 0
        500 http://gb.archive.ubuntu.com/ubuntu/ precise/main amd64 Packages

grub-pc version is:
grub-pc:
  Installed: 1.99-21ubuntu3.1
  Candidate: 1.99-21ubuntu3.1
  Version table:
 *** 1.99-21ubuntu3.1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ precise-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     1.99-21ubuntu3 0
        500 http://gb.archive.ubuntu.com/ubuntu/ precise/main amd64 Packages

kernel version is:
Linux DTC141 3.2.0-23-generic #36-Ubuntu SMP Tue Apr 10 20:39:51 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-3.2.0-23-generic 3.2.0-23.36
ProcVersionSignature: Ubuntu 3.2.0-23.36-generic 3.2.14
Uname: Linux 3.2.0-23-generic x86_64
NonfreeKernelModules: talpa_vfshook talpa_pedconnector talpa_pedevice talpa_vcdevice talpa_core talpa_linux talpa_syscallhook
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 2.0.1-0ubuntu11
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: dtc-admin 5475 F.... pulseaudio
CRDA: Error: command ['iw', 'reg', 'get'] failed with exit code 1: nl80211 not found.
Card0.Amixer.info:
 Card hw:0 'PCH'/'HDA Intel PCH at 0xe1a60000 irq 46'
   Mixer name : 'Intel CougarPoint HDMI'
   Components : 'HDA:10ec0269,1028047e,00100100 HDA:80862805,80860101,00100000'
   Controls : 32
   Simple ctrls : 15
Date: Fri Jul 20 15:40:36 2012
HibernationDevice: RESUME=UUID=fa6b0036-8d86-4d42-bf3c-f932c1a206f7
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
IwConfig:
 lo no wireless extensions.

 eth0 no wireless extensions.
MachineType: Dell Inc. OptiPlex 990
ProcEnviron:
 SHELL=/bin/bash
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_GB.UTF-8
 LANGUAGE=en_GB:en
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.2.0-23-generic root=UUID=4081d15c-83a5-4688-9487-a67293594616 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.2.0-23-generic N/A
 linux-backports-modules-3.2.0-23-generic N/A
 linux-firmware 1.79
RfKill:

SourcePackage: linux
StagingDrivers: mei
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/28/2011
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A05
dmi.board.name: 0D6H9T
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 15
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA05:bd05/28/2011:svnDellInc.:pnOptiPlex990:pvr01:rvnDellInc.:rn0D6H9T:rvrA00:cvnDellInc.:ct15:cvr:
dmi.product.name: OptiPlex 990
dmi.product.version: 01
dmi.sys.vendor: Dell Inc.

[penalvch (penalvch)]

/var/log/syslog cut from Bug Description.

[penalvch (penalvch)]

Eoin, thank you for reporting this bug and helping make Ubuntu better. If you could also please test the latest upstream kernel available that would be great. It will allow additional upstream developers to examine the issue. Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Once you've tested the upstream kernel, please remove the 'needs-upstream-testing' tag. This can be done by clicking on the yellow pencil icon next to the tag located at the bottom of the bug description and deleting the 'needs-upstream-testing' text. As well, please comment on which kernel version specifically you tested.

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'.

If you are unable to test the mainline kernel, for example it will not boot, please add the tag: 'kernel-unable-to-test-upstream', and comment as to why specifically you were unable to test it.

Please let us know your results. Thanks in advance.

[Luis Henriques (henrix)]

In addition to what's referred in comment #3, it looks like you're using "TALPA Filesystem Interceptor". Is this bug reproducible is you uninstall it? I believe you installed it manually, and from your logs its very likely to be a bug on it.

[Eoin (eoin-malins)]

henrix++; Having appeared to have to have nailed the problem by spotting the "TALPA Filesystem Interceptor". I installed Sophos anti-virus for linux v7 and TALPA appears to have been part of it. The problem is no longer reproducible having uninstalled sophos. I have tried this on several machines and they are no longer having problems with update-grub.

dtc-admin@DTC141:/opt/sophos-av$ update-grub
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-3.2.0-25-generic
Found initrd image: /boot/initrd.img-3.2.0-25-generic
Found linux image: /boot/vmlinuz-3.2.0-23-generic
Found initrd image: /boot/initrd.img-3.2.0-23-generic
Found memtest86+ image: /boot/memtest86+.bin
/usr/lib/os-probes/50mounted-tests: line 92: 15723 Killed grub-mount "$partition" "$tmpmnt" 2> /dev/null
/usr/lib/os-probes/50mounted-tests: line 92: 15743 Killed grub-mount "$partition" "$tmpmnt" 2> /dev/null
done

root@localhost:/opt/sophos-av# ./uninstall.sh
Uninstalling Sophos Anti-Virus.
WARNING: Sophos Anti-Virus still running.
Do you want to stop Sophos Anti-Virus? Yes(Y)/No(N) [N]
> y

Stopping Sophos Anti-Virus.
Sophos Anti-Virus has been uninstalled.
root@localhost:/opt/sophos-av#

root@localhost:/opt/sophos-av# logout

dtc-admin@localhost:/opt$ sudo update-grub
[sudo] password for dtc-admin:
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-3.2.0-25-generic
Found initrd image: /boot/initrd.img-3.2.0-25-generic
Found linux image: /boot/vmlinuz-3.2.0-23-generic
Found initrd image: /boot/initrd.img-3.2.0-23-generic
Found memtest86+ image: /boot/memtest86+.bin
Found Windows 7 (loader) on /dev/sda1
done
dtc-admin@localhost:/opt$

Many thanks to everyone for their interest and insight into this. Especially to henrix, to whom I now owe a pint.
E.

[Luis Henriques (henrix)]

Great, I'll change the status of the bug to 'Invalid'.

(By the way, I won't forget about that pint!)