access to nbd-mounted volume causes kernel panic, oops, shock and death

[qmax]

Clients:
various, with Ubuntu 10.04.1 LTS i386 (desktop), or 10.04.2 LTS i386 (installed as terminal-client)
Last tested Ethernet Controller: nVidia Corporation MCP61 Ethernet (forcedeth driver)

Server:
DistroRelease: Ubuntu 10.04
InstallationMedia: Ubuntu-Server 10.04 LTS "Lucid Lynx" - Release amd64 (20100427)
Package: nbd-server 1:2.9.14-2ubuntu1
PackageArchitecture: amd64
ProblemType: Bug
ProcEnviron:
  LANG=en_US.UTF-8
  SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.32-30.59-server 2.6.32.29+drm33.13
SourcePackage: nbd
Tags: lucid
Uname: Linux 2.6.32-30-server x86_64
Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller
(driver r8169 driver)

Steps to reproduce:
on server:
mkdir /var/tmp/cargo
dd if=/dev/urandom of=/var/tmp/cargo/1 bs=1048576 count=128
dd if=/dev/urandom of=/var/tmp/cargo/2 bs=1048576 count=128
dd if=/dev/urandom of=/var/tmp/cargo/3 bs=1048576 count=128
dd if=/dev/urandom of=/var/tmp/cargo/4 bs=1048576 count=128
mksquashfs /var/tmp/cargo /var/tmp/cargo.img -noI -noD -noF -b 4096 # image size is 513Mb, comparable with LTSP image
nbd-server 2000 /var/tmp/cargo.img -C /dev/null -r

on client:
nbd-client ${SERVER_IP} 2000 /dev/nbd0 # tried with options bs=4096 and bs=1024
mount -o ro -t squashfs /dev/nbd0 /var/tmp/nbdtmp
while true; do cat /var/tmp/nbdtmp/* > /dev/null; done # any access will trigger

expected:
succesfull mounted volume on client;
in reproducing scenario: high load of cpu making stupid things in endless, but interruptable process
in ltsp booting: ltsp_nbd boot scenario to continue after mounting root device

observed:
mounted with "nbd0: unknown partition table in kernel.log"
random kernel segfaults, Oops, panic, and some_random_application Tainted: P
stack trace is different each time, at time of reporting bug it failed to get logged.
attaching kernel log as an example

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: nbd-client 1:2.9.14-2ubuntu1
ProcVersionSignature: Ubuntu 2.6.32-27.49-generic 2.6.32.26+drm33.12
Uname: Linux 2.6.32-27-generic i686
NonfreeKernelModules: nvidia
Architecture: i386
Date: Tue Apr 12 18:13:48 2011
ProcEnviron:
 LANGUAGE=
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: nbd

[Dave Gilbert (ubuntu-treblig)]

Kernel oopsed, so I reckon this is best in the linux package (even if it did happen in response to being tickled by nbd).

You'll probably get some mails asking for apport information etc and possibly to try other kernels.

[Brad Figg (brad-figg)]

This bug is missing log files that will aid in diagnosing the problem. From a terminal window please run:

apport-collect 758689

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Joseph Salisbury (jsalisbury)]

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v3.6 kernel[0] (Not a kernel in the daily directory) and install both the linux-image and linux-image-extra .deb packages.

Once you've tested the upstream kernel, please remove the 'needs-upstream-testing' tag. Please only remove that one tag and leave the other tags. 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.

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'.
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/v3.6-rc2-quantal/

[Launchpad Janitor (janitor)]

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